Dyslexia reading specialist: what they do and how to find one

Last updated 2026-07-09

What does a dyslexia reading specialist actually do?

A dyslexia reading specialist teaches reading in a completely different way than a classroom teacher does. The core method is structured literacy: explicit, systematic instruction in phonemic awareness, phonics, decoding, fluency, and spelling, sequenced from simple to complex and always multisensory. A student might tap out phonemes while saying them aloud and trace letters at the same time. Every skill is taught directly. Nothing is assumed.

This is not remediation in the "sit with a kid and re-read the same book" sense. Specialists follow a diagnostic-prescriptive model: they assess exactly where a student's phonological processing breaks down, then build a lesson sequence that targets that specific gap. Progress gets measured session by session, more than at report-card time.

They also do a lot of things parents don't expect. A good specialist will read through a student's psychoeducational evaluation with the family, explain what the scores mean, suggest which accommodations to request in an IEP or 504 plan, and write progress reports that schools are legally required to consider. They work as a bridge between the neuropsychology world and the classroom.

Understand one thing clearly: dyslexia is a phonological processing difference. The International Dyslexia Association defines it as "characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities" that "result from a deficit in the phonological component of language." ^[1] A specialist's entire job grows out of that definition. See our overview of the dyslexia definition if you want to ground yourself in what the diagnosis means before you start looking for help.

What credentials should a dyslexia specialist have?

This is where parents get burned most often. The word "specialist" has no legal protection. Anyone can print it on a business card. So look past the title and check the actual credential.

The two credentials that carry real weight are the Certified Academic Language Therapist (CALT) and the Associate Level and Certified Level certifications from the International Dyslexia Association (IDA). The Academic Language Therapy Association governs the CALT: candidates must finish a minimum of 200 supervised clinical hours and pass a written exam. ^[2] IDA's certifications require demonstrated competency across the Knowledge and Practice Standards for Teachers of Reading, which the IDA published and which roughly 30 states have now adopted or referenced in dyslexia legislation. ^[3]

Orton-Gillingham (OG) training by itself is not a credential. A practitioner can take a weekend OG workshop and technically claim OG training. What you want is someone who completed a supervised practicum of at least 100 hours under a Fellow of the Academy of Orton-Gillingham Practitioners and Educators (AOGPE). Fellows and Associates of AOGPE have passed a demanding multi-year certification process. ^[4]

Here's how the credential landscape stacks up in practice:

Credential	Governing Body	Min. Supervised Hours	Exam Required?
CALT	ALTA	200 clinical hours	Yes
IDA Certified (CERI/CALT-QI)	IDA	Varies by program	Yes
AOGPE Associate	AOGPE	100+ practicum hours	Yes
AOGPE Fellow	AOGPE	500+ hours	Yes
Wilson Reading Cert.	Wilson Language	160 practicum hours	Yes
Basic OG Workshop	Varies	0 supervised	No

Ask every candidate which credential they hold, who issued it, and how many supervised hours it took. If they can't answer clearly, keep looking.

For context on the different subtypes of dyslexia a specialist should be able to address, see phonological dyslexia and surface dyslexia.

How much does a private dyslexia specialist cost?

Private dyslexia specialist sessions usually run $80 to $200 per hour across most U.S. markets, with rates higher in major metro areas and lower in rural regions. Nobody publishes a national survey with clean averages, so that range comes from publicly listed rates at certified tutoring practices and parent community data, not a peer-reviewed study. The honest answer: rates vary enough that you should call three providers in your area before assuming any number.

Most specialists recommend two to three sessions per week, at minimum, for real progress. That puts a full school year of private intervention at $5,000 to $20,000 depending on frequency and rate. That's a real number that real families face.

Some ways to bring the cost down:

University training clinics often charge $20 to $50 per session because graduate students deliver the lessons under licensed supervision. Quality is usually fine for mild-to-moderate cases. Search for programs run by a university's speech-language pathology or education department.

Group instruction from a certified specialist costs less per student, sometimes $40 to $80 per session. Research from the Florida Center for Reading Research and elsewhere shows small-group structured literacy is nearly as effective as 1:1 for most students with dyslexia, as long as the group is 3 students or fewer and the instructor is truly certified. ^[5]

Public school services are free under IDEA if your child qualifies for special education, or free under Section 504 if accommodations are the main need. If the school refuses to provide a specialist and the evaluation shows a reading disability, that refusal may be a FAPE violation. More on that in the school rights section below.

What does structured literacy instruction actually look like?

Parents hear "structured literacy" constantly. Few can describe a real session.

A typical 45-to-60-minute session with a certified specialist follows a predictable order. The first 5 to 10 minutes are review: the student practices previously learned phoneme-grapheme correspondences using drill cards, going both directions (sound to symbol, symbol to sound). This isn't busywork. Automaticity in decoding gets built by repeated, timed retrieval, not by reading in context.

Then comes new learning: one new phonics concept introduced explicitly. The specialist names the concept, shows its visual pattern, demonstrates the sound, and has the student produce it while tapping or using another kinesthetic anchor. No guessing. No using pictures for context clues.

Word-level reading and spelling follow. The student reads lists of real and nonsense words that use the day's pattern, then spells dictated words. Nonsense words matter here because they test pure decoding and stop the student from reading by memory.

Last comes connected text practice: a decodable passage where most words follow patterns the student has already mastered. This builds fluency without forcing the student to guess at words above their current level.

The International Dyslexia Association's structured literacy framework names six language levels: phonology, sound-symbol association, syllable instruction, morphology, syntax, and semantics. ^[1] A good specialist works all six, more than phonics alone. Morphology instruction (understanding that "un+happy" means not happy) becomes especially important around third grade and above.

For a look at how dyslexia shows up day-to-day, which can help you understand what your child is working against, see what does dyslexia look like.

Does my child need a diagnosis before seeing a specialist?

No. A formal diagnosis is not required to start with a private specialist. Any child who struggles to read can begin structured literacy instruction whether or not a psychoeducational evaluation has happened.

That said, a full evaluation matters for school rights. Under the Individuals with Disabilities Education Act (IDEA), a school must provide a free and appropriate public education (FAPE) to every eligible student with a disability, and dyslexia is a covered condition. The statute at 20 U.S.C. § 1400 et seq. governs this. ^[6] To reach school-based services, you usually need an evaluation that documents a reading disability. The school must run this evaluation for free if you request it in writing and they agree there's reason to assess. They have 60 days from getting your consent to finish it (some states use a shorter timeline).

Private specialists will usually run their own informal reading assessments at the first session, often using tools like the DIBELS 8th Edition, the Phonological Awareness Literacy Screening (PALS), or the GORT-5. These aren't the same as a full psychoeducational battery, but they're enough to start instruction.

If you're wondering whether your child might have dyslexia before you've seen anyone, our dyslexia test overview explains what screening tools look at and where they fall short. For the early warning signs, signs of dyslexia covers the developmental red flags by age.

What are my child's school rights for dyslexia specialists?

This is the section most parents need most and understand least.

IDEA (20 U.S.C. § 1400) requires schools to provide FAPE: a free, appropriate public education in the least restrictive environment. ^[6] "Appropriate" got defined more sharply by the Supreme Court in Endrew F. v. Douglas County School District (2017), which held that a school's program must be "reasonably calculated to enable a child to make progress appropriate in light of the child's circumstances." ^[7] That standard sits higher than the old "more than de minimis" floor. If your child's school offers pullout reading support twice a week with a general education aide who has no dyslexia training, and your child makes no measurable progress, that's an argument worth making in an IEP meeting.

Here's what you can request:

You can ask that the IEP specify the type of reading instruction (for example, "structured literacy using an Orton-Gillingham-based program") rather than leaving it vague. Schools sometimes resist this because it limits their discretion. Push anyway. The more specific the IEP, the more accountable the school.

You can request a reading specialist with documented dyslexia training as the service provider. Many states now have dyslexia laws that go further than IDEA. The National Center on Improving Literacy lists state-by-state dyslexia laws and their requirements. ^[8]

Section 504 of the Rehabilitation Act applies when a student doesn't qualify for special education but has a disability that substantially limits a major life activity. Reading counts as a major life activity. A 504 plan can require extended time, decodable text materials, or audiobook access, but it can't compel specialized instruction the way an IEP can.

If the school denies an evaluation or refuses services you believe are warranted, you have the right to request an Independent Educational Evaluation (IEE) at school expense. The U.S. Department of Education's Office of Special Education Programs confirms this right on its IDEA site. ^[6]

Document everything in writing. Requests made out loud don't start legal timelines.

How long does specialist intervention take before a child makes real progress?

Honest answer: slower than most parents hope, faster than doing nothing.

Research by Torgesen and colleagues in the Journal of Learning Disabilities found that intensive reading intervention (80 minutes per day for 8 weeks) produced significant gains in word reading for students with severe reading disabilities, with some students moving from the 2nd to the 10th percentile in that window. ^[9] That's meaningful but not dramatic. The same study found that word reading fluency, the actual speed of reading, improved more slowly than accuracy.

For typical outpatient private tutoring at two sessions per week, most certified specialists talk about 1 to 2 years before a student reaches grade-level fluency, assuming the gap isn't enormous. Students with deeper phonological processing deficits, particularly those with a double deficit dyslexia profile involving both phonological awareness and rapid naming weaknesses, generally take longer.

Age matters. The brain is more plastic in the early elementary years. A child who starts structured literacy in kindergarten or first grade has a genuinely better prognosis than one who starts in fifth grade. This is one of the most consistently replicated findings in reading research, backed by longitudinal neuroimaging studies from Shaywitz and colleagues showing that early intervention produces measurable changes in brain activation patterns. ^[10]

None of this means older kids can't improve. They absolutely can. It just means you shouldn't wait.

Progress should get tracked with repeated oral reading fluency probes (like DIBELS ORF) every 4 to 8 weeks. If a student isn't gaining at least 1.5 words per minute per week in oral reading fluency across a 10-week period, the approach or the intensity needs to change. That benchmark comes from research-based guidelines used by reading intervention programs nationwide. ^[5]

What questions should I ask before hiring a dyslexia specialist?

You're hiring someone to do a high-stakes job. Ask real questions.

First, ask about credentials specifically: "What certification do you hold, who issued it, and how many supervised clinical hours did it require?" A legitimate specialist answers this without hesitation.

Second, ask about their assessment process: "Before we start, how will you figure out where my child is and what needs to be addressed?" They should describe a structured informal reading inventory or a standardized screening tool, more than "I'll observe them reading."

Third, ask what program they use: "Is it Orton-Gillingham, Wilson Reading System, Barton, SPIRE, or something else?" They should name the program and explain why they chose it. All of those are structured literacy programs with meaningful research behind them. Barton Reading and Spelling is the program most commonly used by trained parent-tutors, and it's popular in the homeschool dyslexia community. Wilson Reading System shows up widely in schools. There is no single "best" program; what matters is fidelity of implementation.

Fourth, ask about communication: "How often will you send me progress notes, and what data will they include?" You want written notes with word reading accuracy percentages, oral reading fluency scores, and specific skills mastered, more than "she did great today."

Fifth, ask the uncomfortable one: "What would make you recommend I stop working with you and try a different approach or provider?" Good specialists know the limits of their method. Anyone who can't answer this is a red flag.

For families who want to support instruction at home between sessions, the ReadFlare free reading toolkit includes decodable practice materials and a phonics scope-and-sequence tracker to keep you aligned with what the specialist is teaching.

Are online dyslexia specialists effective, or should I find someone in person?

Online instruction over video is genuinely effective for dyslexia intervention. This was a contested claim before 2020. It's much less contested now.

A systematic review by Wood and colleagues in Annals of Dyslexia (2018) examined technology-mediated reading interventions and found that digital delivery of structured literacy programs produced effect sizes comparable to in-person delivery when instructor quality and session frequency were held constant. ^[11] The key variable was the instructor, not the delivery method.

In practice, online sessions work well for older students (roughly second grade and up) who can hold attention on a screen and don't need heavy hands-on tactile materials. For kindergartners and first graders, in-person is usually better because tactile letter trays, sand boxes, and physical manipulatives make up a bigger part of the lesson.

The main reason to prefer online: access. Most rural families and many urban families simply can't find a CALT or AOGPE-certified specialist within driving distance. Online opens a national pool of providers. Directories to search include the IDA's provider database and the ALTA member directory.

One practical tip: ask the specialist to mail a physical materials packet before the first session. Many online OG specialists do this routinely, shipping letter tiles and decodable readers to the family before session one.

How is a dyslexia reading specialist different from a regular reading teacher or tutor?

This distinction matters more than most people realize.

A reading teacher or general literacy coach is trained to teach reading to the broad population of students, using a mix of approaches. Many were trained in balanced literacy or guided reading frameworks, which lean on context clues and pictures to identify words. For students with dyslexia, those strategies often work against progress, because dyslexia is at its core a phonological decoding problem. ^[1] Guessing from context is a coping strategy, not a fix.

A dyslexia specialist is trained specifically in the neurological and linguistic basis of dyslexia and in the structured literacy interventions with the strongest evidence for that population. The training gap is large. A general reading endorsement in most states requires roughly 12 to 18 credit hours of coursework. The CALT requires 200 supervised clinical hours on top of graduate-level coursework in language structure. ^[2]

This is not a knock on classroom teachers, many of whom are excellent and deeply committed. It's a statement about preparation for a specific need. You wouldn't expect a general practitioner to do neurosurgery. The skill set for teaching phonological decoding to a student with dyslexia is specialized and takes years to build.

For a parent who wants to understand the range of subtypes their child's specialist should know, see types of dyslexia and visual dyslexia for how different profiles call for different instructional emphases.

What does the research say about structured literacy for dyslexia?

The evidence is strong enough that the argument is essentially over among reading scientists, even if it hasn't fully reached classrooms.

The National Reading Panel's 2000 report to Congress, produced by the National Institute of Child Health and Human Development, concluded that explicit, systematic phonics instruction produces significant benefits in word reading for all students and especially for those at risk. ^[12] That report analyzed 38 controlled studies. That was 2000. The evidence has only piled up since.

The most cited work in this space is the research program of Sally Shaywitz at Yale, whose neuroimaging studies showed that students with dyslexia activate different neural pathways during reading than typical readers, and that after intensive phonics-based intervention, brain activation shifts toward the patterns seen in skilled readers. ^[10] This gets quoted directly in the 2020 edition of her book "Overcoming Dyslexia," but the underlying journal papers run in journals like Biological Psychiatry and PNAS.

For practicing specialists, the key applied research is the work of Torgesen and colleagues (2001) showing that intensive intervention can produce average-level word reading in many students previously considered severely reading disabled, plus longitudinal work from the Florida Center for Reading Research showing that Tier 3 intensive structured literacy produces gains of 1.5 to 2.0 standard deviations in phonological awareness. ^[5][9]

One honest caveat: most of this research is on phonological accuracy. Reading fluency, the speed and automaticity of reading, responds more slowly to intervention. Students with dyslexia often reach accurate decoding while staying slower readers than peers, even after years of good instruction. That's not a failure of the method. It reflects the nature of the underlying neurological difference.

The ReadFlare parent advocacy kit includes a one-page research summary you can bring to an IEP meeting to make the case for structured literacy services at school.

How do I find a qualified dyslexia specialist near me?

Start with the right directories, not a plain Google search.

The International Dyslexia Association runs a provider directory where you can search by zip code and filter by credential. The Academic Language Therapy Association keeps a member directory that lists CALTs and CALIs (Clinical Associates). These are the two most reliable starting points. ^[2][3]

If you can't find a certified provider locally, the Academy of Orton-Gillingham Practitioners and Educators (AOGPE) has a practitioner directory on its site. ^[4] Wilson Language Training keeps a list of certified Wilson Reading System practitioners.

For school-based services, your child's district may have reading specialists on staff, but their credentials vary widely by state and district. You have the right to ask specifically about a staff member's dyslexia training as part of any IEP discussion.

Before you hire anyone, ask for one free or low-cost observation session. Most legitimate specialists let a parent watch a session. If a provider refuses to let you observe, that's a problem.

Also ask for two or three references from current or recent families, specifically families whose children had a similar profile to yours. Call those references and ask directly: did your child make measurable progress, and how do you know?

For families still researching whether their child's challenges fit the dyslexia profile before hiring anyone, what causes dyslexia explains the genetic and neurological basis, which can help you understand what a specialist is targeting.

Frequently asked questions

What is a dyslexia reading specialist?

A dyslexia reading specialist is a trained educator who delivers structured literacy instruction built for students with phonological processing difficulties. They use explicit, multisensory methods, usually Orton-Gillingham-based programs, to teach decoding, spelling, and fluency. Unlike general reading tutors, they hold credentials like CALT or IDA certification and base their work on the neurological science of dyslexia.

How do I know if my child needs a dyslexia specialist and more than regular tutoring?

If your child has already tried general reading help without steady progress, struggles specifically with sounding out unfamiliar words, confuses similar letter sounds, or reads very slowly despite effort, a specialist is the better choice. General tutors typically re-teach grade-level content. Specialists address the underlying phonological processing difference. If your child has a formal or suspected dyslexia diagnosis, a certified specialist is the right level of support.

Can my child's school be required to provide a dyslexia specialist?

Under IDEA (20 U.S.C. § 1400), schools must provide a free and appropriate public education to students with disabilities, including dyslexia. If your child qualifies for special education, the IEP can specify specialized reading instruction from a trained provider. You can ask the school to describe the credentials of the reading staff in the IEP. If services are inadequate and progress is stalled, you can request an Independent Educational Evaluation at the school's expense.

What is the difference between a CALT and an Orton-Gillingham practitioner?

CALT (Certified Academic Language Therapist) is issued by the Academic Language Therapy Association and requires 200 supervised clinical hours plus an exam. Orton-Gillingham is a teaching approach, not a credential. Someone can attend a basic OG workshop with no supervised hours and claim OG training. What matters is whether an OG practitioner is also credentialed through AOGPE, IDA, or ALTA, which all require documented supervised practice and testing.

What programs do dyslexia specialists typically use?

The most widely used programs are Wilson Reading System, Barton Reading and Spelling, Orton-Gillingham (direct method), SPIRE (Specialized Program Individualizing Reading Excellence), and LIPS (Lindamood Phoneme Sequencing). All are structured literacy programs with systematic phonics sequences, multisensory components, and decodable text. The quality of the instructor matters more than which specific program they use, as long as it's a genuine structured literacy approach.

At what age should a child start seeing a dyslexia specialist?

As early as possible. Research shows brain plasticity is highest in kindergarten through second grade, and early structured literacy intervention produces better and faster outcomes than intervention starting in middle school. If your child is in first or second grade and not mastering phonics at the expected pace, don't wait for the school to act. A specialist evaluation and early intervention are appropriate even before a formal diagnosis is in place.

Can a parent learn to do Orton-Gillingham tutoring at home instead of hiring a specialist?

Yes, with significant caveats. Programs like Barton Reading and Spelling are built for parent delivery and include training videos. This works best for mild-to-moderate cases and motivated parents with steady time to practice. A trained specialist will deliver better instruction than most parents can manage, but parent-delivered Barton is far better than no structured literacy at all. For severe cases or students who have multiple years of reading gap, professional delivery is strongly preferable.

What does rapid naming have to do with dyslexia, and does a specialist address it?

Rapid automatized naming (RAN) is the speed at which a person can name a series of familiar symbols like letters or numbers. Students with weaknesses in both RAN and phonological awareness have what researchers call double-deficit dyslexia, and they tend to have the most persistent reading difficulties. Good specialists assess RAN and adjust fluency-building expectations accordingly. RAN deficits respond more slowly to intervention than phonological awareness deficits do. See our article on rapid naming deficit for more detail.

Does dyslexia intervention also help with math or is that separate?

Dyslexia intervention focuses on language-based reading skills and doesn't directly address math calculation difficulties. Many students with dyslexia also have dyscalculia, sometimes called number dyslexia or math dyslexia, which is a separate profile requiring its own targeted intervention. A good psychoeducational evaluation will screen for both. If your child struggles with reading and math, ask whether both areas were assessed and whether both need separate support plans.

How do I tell if the specialist my child is seeing is actually working?

Ask for data, not impressions. You want oral reading fluency scores (words read correctly per minute) measured every 4 to 8 weeks with a standard probe like DIBELS ORF, plus phonics skills checklists showing which patterns have been mastered. Research-based benchmarks suggest at least 1.5 words-per-minute-per-week growth in oral reading fluency for an intervention to count as effective. If your specialist can't show you a graph of progress over time, that's a problem worth raising directly.

What should an IEP say to ensure my child gets proper dyslexia reading support?

The IEP's present levels section should document the specific reading deficits, more than a label. Goals should be measurable: "By May, student will read 90 WCPM on a third-grade probe with 95% accuracy." The services section should specify the type of instruction (structured literacy, OG-based), frequency (at least 3 times per week for 45 minutes), and the qualifications of the provider. Vague language like "reading support" with no program or credential named gives the school maximum flexibility and you minimum accountability.

Is dyslexia instruction covered by FSA or HSA accounts?

Generally no. FSA and HSA funds cover medical expenses as defined by IRS Publication 502, and tutoring for learning disabilities isn't on that list unless it's provided by a licensed medical or health professional as part of treatment for a medical condition. Some families have used these funds for services from a licensed speech-language pathologist treating a language-based reading disorder, but this area is complex and you should consult a tax professional before assuming reimbursement will be approved.

My child was denied a school evaluation for dyslexia. What can I do?

If a school denies your written evaluation request, they must give you a prior written notice (PWN) explaining the reasons. You can then request mediation, file a state complaint with your state's department of education, or request a due process hearing under IDEA. The U.S. Department of Education's special education office has information on your procedural rights. Many states also have parent training and information centers that offer free advocacy support.

Can a dyslexia specialist help with spelling as well as reading?

Yes, and this is one of the clearest wins of structured literacy. Spelling and decoding are two sides of the same phonics coin: reading maps print to sound, spelling maps sound to print. Structured literacy programs teach both at once. Many students with dyslexia find that spelling improves faster than reading fluency once they're in a properly structured program, because spelling is more rule-governed and less dependent on reading speed.

Sources

1. International Dyslexia Association, Definition of Dyslexia: Dyslexia is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities resulting from a deficit in the phonological component of language; structured literacy framework specifies six language levels.
2. Academic Language Therapy Association (ALTA), CALT Certification: CALT candidates must complete a minimum of 200 supervised clinical hours and pass an exam.
3. International Dyslexia Association, Knowledge and Practice Standards: IDA certifications require demonstrated competency across the Knowledge and Practice Standards for Teachers of Reading, referenced in approximately 30 states' dyslexia legislation.
4. Academy of Orton-Gillingham Practitioners and Educators (AOGPE): AOGPE Associates must complete 100+ supervised practicum hours; Fellows must complete 500+ hours and pass a multi-year certification process.
5. Florida Center for Reading Research: Small-group structured literacy (3 students or fewer) is nearly as effective as 1:1 instruction; Tier 3 intensive structured literacy produces gains of 1.5 to 2.0 standard deviations in phonological awareness; benchmark for effective intervention is at least 1.5 words per minute per week growth in oral reading fluency.
6. U.S. Department of Education, Office of Special Education Programs (OSEP), IDEA: IDEA (20 U.S.C. § 1400) requires schools to provide a free and appropriate public education (FAPE) to eligible students with disabilities; students have the right to an Independent Educational Evaluation at school expense if they disagree with the school's evaluation.
7. Supreme Court of the United States, Endrew F. v. Douglas County School District, 580 U.S. 386 (2017): The Supreme Court held that a school's program must be 'reasonably calculated to enable a child to make progress appropriate in light of the child's circumstances,' raising the FAPE standard above de minimis.
8. National Center on Improving Literacy, State Dyslexia Laws: Lists state-by-state dyslexia laws and their requirements; funded by the U.S. Department of Education.
9. Torgesen J.K. et al. (2001), Journal of Learning Disabilities, Intensive remedial instruction for children with severe reading disabilities: Intensive reading intervention (80 min/day for 8 weeks) produced significant word reading gains, with some students moving from 2nd to 10th percentile; fluency improved more slowly than accuracy.
10. Shaywitz S.E. et al., neuroimaging studies on dyslexia intervention, PNAS: After intensive phonics-based intervention, brain activation in students with dyslexia shifts toward patterns seen in skilled readers; early intervention produces measurable changes in neural activation patterns.
11. Wood S.G. et al. (2018), Annals of Dyslexia, Technology-mediated reading interventions: Digital delivery of structured literacy programs produced effect sizes comparable to in-person delivery when instructor quality and session frequency were held constant.
12. National Institute of Child Health and Human Development (NICHD), National Reading Panel Report (2000): Explicit, systematic phonics instruction produces significant benefits in word reading for all students and especially for those at risk; analysis covered 38 controlled studies.