Risperidone and Autism Ranking:

There are a number of limitations to all of the research studies published to date. For example

Approximately half of the studies used single-case designs, that is, they did not have a control group of participants who did not receive risperidone.
Four of the single case design studies used relatively weak methodologies - such as non-experimental case series.
Four of the randomised controlled studies were non-blinded.
Some of the randomised, controlled studies did not follow methodologies expected within a randomised controlled trial. For example, the study by Ghanizadeh et al (2013) did not provide details of the randomisation and allocation concealment process used.

Six of these single case design studies included fewer than 10 autistic participants.
Four of the randomised controlled studies had fewer than thirty autistic participants.
Some of the studies had a high dropout rate. For example, one study (McDougle et al, 1998) had a dropout rate of 33% (with 7 of 21 participants being unable to complete the treatment).
Some of the studies examined participants with a range of conditions, only a proportion of whom were autistic. For example, the study by Tyrer et al, 2008 had 86 participants but only 14 of these were classed as being autistic.
Some of the studies were restricted to specific groups of participants. For example, one study (Alexander et al, 2004) looked only at adults with Asperger syndrome.
Some of the studies (such as King et al, 2003) did not appear to have independently verified the diagnosis of autism using established diagnostic tools like the ADOS or ADI-R.

Some of the studies gave very little detail about the risperidone and how it was administered. For example, Lemmon et al, 2011 did not state the length of treatment, the frequency of treatment or the dosage of risperidone that was given to the participants.
Some of the studies (such as Mukaddes et al, 2004) lasted for relatively short periods of time (six weeks) and did not appear to follow up the participants once the treatment had completed.
One of the studies (Fayyazi et al, 2013) used a crossover design (alternating between risperidone and buspirone) but provided insufficient details about the washout period (the period when no medication was provided) between the medications.

Some of the group studies had unevenly matched participant groups. For example, in the study by Luby et al (2006) the group of pre-schoolers treated with risperidone showed significantly greater severity of autism symptoms at baseline than the group which received the placebo.

Some of the studies used a small number of outcome measures and/or used less robust outcome measures. For example McDougle et al, 1997 used only one outcome measure, the Clinical Global Impression Scale. This is less robust than some other measures because it relies on the subjective judgement of the clinician.
Some of the studies did not provide adequate data on the baseline and outcome characteristics of the participants. For example, Vercellino et al (2001) used three different behavioural measures for the participants but did not provide detailed, tabulated data for any of these measures at the baseline or at the endpoint of the study.
Some of the studies (such as Ghaeli et al, 2014) did not report objective measures of potential adverse side effects (such as changes to blood glucose levels etc.) but relied on the participants to report their subjective views of any adverse side effects.
Some of the studies did not identify if risperidone had any beneficial effects in the medium to long term (six months or longer).

Very few of the studies appeared to involve autistic people or parents and carers in the design, development and evaluation of those studies.
Some of the studies (such as Shea et al, 2004) were funded by Janssen-Ortho Inc, a manufacturer of one of the commercial brands of risperidone. The researchers involved may therefore have been biased towards the intervention, however unconsciously.

For a comprehensive list of potential flaws in research studies, please see "Why some autism research studies are flawed."

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