Study finds little evidence on effectiveness of common antidepressant in autism spectrum disorders

Reviewed by Kate Anderton, B.Sc. (Editor)Oct 23 2019

A new study has found there is little evidence that a widely used antidepressant is effective at reducing obsessive compulsive behaviours in children and adolescents with autism spectrum disorders.

The research, led by the Murdoch Children's Research Institute (MCRI) and published in the latest edition of The Journal of the American Medical Association, found taking fluoxetine (also known as Prozac) for 16 weeks failed to significantly lower the frequency and severity of obsessive compulsive behaviours in children with autism spectrum disorders including autism, Asperger's syndrome and pervasive developmental disorder (PDD).

MCRI paediatrician Professor Dinah Reddihough said:

More than half of children and adolescents with autism spectrum disorders are prescribed medication, with up to one third receiving antidepressants despite inconclusive evidence of their effectiveness.

The randomised clinical trial involved 146 participants, aged between 7.5-18 years, recruited from The Royal Children's Hospital, The Sydney Children's Hospitals Network and the State Child Development Centre, in Perth. They were randomly assigned to receive either fluoxetine or a placebo.

While initial results showed some behavioural improvements, Professor Reddihough said additional analyses revealed no significant difference between the groups, which should be given more weight because it corrects for any imbalances in the data.

"While this is a study with negative findings, it is an important addition to the evidence base for deciding when and when not to prescribe psychoactive medications."

Potential limitations of the study were the high dropout rate due to perceived failure of treatment and adverse reactions being attributed to the medication despite the fact the medication may not have been responsible.

Professor Reddihough said while the evidence was not strong enough to recommend fluoxetine as a treatment we couldn't exclude that it's helpful for some children.

"If parents have any concerns about the use of fluoxetine they should speak with their health professional before changing any treatment plan," she said.

Professor Reddihough said autism spectrum disorders are characterised by impairments in communication and social relatedness and restricted and repetitive interests and behaviours.

About one in 70 Australians are diagnosed with autism spectrum disorder, with boys four times more likely to be diagnosed than girls.

"The lifelong effects of the condition are a significant health disability burden for individuals and their families," she said.

"Restricted, repetitive and stereotypic behaviours frequently interfere with everyday functioning and include ritualistic behaviours, unusual sensory interests, and difficulty coping with change, which often manifests as anxiety, irritability, aggression and self-injury."