The antidepressant Prozac may alleviate repetitive behavior and obsessive-compulsive symptoms in adults with autism, reducing these defining symptoms of the disorder, according to new research.
The research, which included 37 high-functioning autistic adults, mainly diagnosed with Asperger’s syndrome, followed participants for 12 weeks. Taking Prozac (fluoxetine) doubled the chances that a patient would show overall improvement, measured by their clinicians. Half of the participants taking Prozac had significant reductions in obsessive-compulsive symptoms, compared with 8% taking placebo. Side effects were mild to moderate and participants taking Prozac did not show increases in suicidal thoughts or ideas.
“Repetitive behavior is a core symptom of the illness,” says lead author Dr. Eric Hollander, medical director of the Autism and Obsessive-Compulsive Spectrum Program at Montefiore Medical Center in New York, explaining that “from a very early age, these children have rituals and routines. For example, they like to line up their toys and they get very bent out of shape if there is any deviation.”
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A previous, larger study of a similar medication, Celexa (citalopram), in autistic children did not find a reduction in repetitive behaviors, but the drug did reduce irritability and was superior to placebo among children who had the highest levels of irritability. Irritability can sometimes lead to repetitive behaviors because autistic people often engage in these activities to soothe themselves.
Both Prozac and Celexa belong to a class of antidepressants known as selective serotonin reuptake inhibitors, or SSRIs. Prior research on SSRIs in autistic people has also looked at Luvox (fluvoxamine) and found a reduction in repetitive behavior in adults but not children. It is not known if the differences between these studies are due to differences between the medications or other factors.
Obsessive behaviors may also arise in autistic people in response to the stress or discomfort of unpredictable situations. “Many of these individuals have expectations for what’s going to happen, and if there is an unexpected deviation, they experience a lot of discomfort and then they do all these kinds of behaviors,” says Hollander. That’s why people with autism may obsessively avoid locations where they previously experienced discomfort, for example, or they may engage in a repetitive habit like washing, checking, counting, touching or tapping.
When taking Prozac, Hollander says, “Patients acknowledge experiencing less discomfort. They’re more able to go outside their comfort zone and to better resist their habits and rituals.” One participant in Hollander’s study was previously too anxious to take the subway or eat in a restaurant, but, when taking Prozac, was able to tolerate these unpredictable environments.
“It takes the edge off,” Hollander explains, noting that the findings were statistically significant and clinically meaningful. “The clinicians could tell that people were doing better not only in terms of OCD symptoms but overall distress and ability to function.”
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The only drugs approved to treat irritability and repetitive behaviors in autistic children are the atypical antipsychotics Risperdal (risperidone) and Abilify (aripiprazole), which tend to have more severe side effects than Prozac does. Those drugs carry significant risk for weight gain, diabetes and movement disorders.
Responding to the research, Yale Child Study Center director Fred Volkmar told WebMD: “The question remains, ‘Is fluoxetine better than risperidone for this symptom?’ It would be interesting to see studies comparing these two drugs head to head.”
Hollander has previously received funding from pharmaceutical companies, but the current study was paid for by a grant from the Food and Drug Administration’s “orphan” drug program. That program funds research on rare conditions with new drugs or those no longer patented that are not likely to be pursued by industry. When the research was originally funded, Hollander says, autism was considered to be a rare condition.
The study was published in the American Journal of Psychiatry.
Maia Szalavitz is a health writer at TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.