Prevalence study of the randomized controlled trials in the Journal of Intellectual Disability Research: 1957-1994.
Half of the ID RCTs you need are hiding in plain sight because old papers lack the right database tags.
01Research in Context
What this study did
The authors hand-searched every issue of the Journal of Intellectual Disability Research from 1957 through 1994.
They wanted to know how many randomized controlled trials, or RCTs, were printed in that span.
They also checked how well electronic databases tagged those RCTs so others could find them later.
What they found
Fifty-six RCTs appeared in the journal during those 37 years.
Most of the trials were not labeled as RCTs in the electronic record, so a simple database search would miss them.
Poor keywords made the papers almost invisible to anyone doing a fast computer search.
How this fits with other research
Wang et al. (2026) later pooled five of these hard-to-find RCTs in a meta-analysis on exercise for kids with ID.
Because the 1997 audit showed the trials were poorly tagged, Aiwei’s team probably had to dig by hand, just like you would.
Anderson et al. (2019) counted U.S. prevalence studies and also noted big data gaps; both papers warn that sloppy indexing hides evidence.
Together they make a clear thread: if you want the full picture on intellectual disability, you cannot trust database filters alone.
Why it matters
When you plan a literature review or prep for an evidence-based staff meeting, run a hand-search through key ID journals instead of relying only on PubMed check-boxes.
You will catch older RCTs that filters miss, strengthen your treatment arguments, and avoid duplicating work that is already done but simply lost in the digital shuffle.
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02At a glance
03Original abstract
Systematic reviews of care are increasingly potent guides to clinical practice, and it is important that all relevant randomized controlled trials (RCTs) are identified by those within the speciality of learning disability who produce such works. All RCTs in the Journal of Intellectual Disability Research and its predecessor were identified by hand-searching (1957-1994), and the frequency, origin, intervention and quality of reporting of randomization were described. Electronic searches for the trials were undertaken for the years 1974-1994, and the quality of indexing was inspected and tested. These electronic searches were then compared to a 'gold standard' search. Fifty-six RCTs were identified. None contained the world 'randomized' in the title and only nine mentioned it in the abstract. Out of the 37 RCTs published between 1974 and 1994, 36 are in PsycLIT and 37 in MEDLINE. One MEDLINE record contained the wrong abstract. The methodological phrases used in the electronic records were poor, and thus, the precision of electronic searches, using both databases, was low. This international journal contains many relevant RCTs from around the world, involving several types of interventions. Unfortunately, these trials cannot be readily accessed electronically using methodological phrases designed to find RCTs. Improved quality of indexing would facilitate identification of RCTs and their dissemination.
Journal of intellectual disability research : JIDR, 1997 · doi:10.1111/j.1365-2788.1997.tb00702.x