New research reveals that the highest rates of depression are seen in individuals with autism who have above average intelligence. This is different to the general population, where lower intelligence is linked to higher rates of depression. (Unsplash/Ben White), CC BY-SA
Until now, researchers and clinicians did not know how many individuals with autism were affected by depression.
Our study, which involved a systematic review of nearly 8,000 research articles, now reveals clear evidence that depression is highly prevalent in both children and adults with autism. It also reveals that depression is more common in individuals with autism who have higher intelligence.
Additional symptoms include loss of interest in activities, physiological changes (e.g. sleep, appetite, or energy disturbance), cognitive changes (e.g. feelings of worthlessness, difficulties with attention) and suicidal thoughts or actions.
Clinicians also have to be particularly careful that they do not confuse the symptoms of depression with the symptoms of autism. For example, people with autism and people with depression have difficulties with social relationships.
The key difference between these groups is why they experience these problems. People with autism often lack the social skills necessary to engage with others. In contrast, people with depression often withdraw from others because they lose the ability to find pleasure in their social interactions.
Higher IQ, higher rates of depression
We found that the highest rates of depression are seen in individuals with autism who have above average intelligence.
While this study did not look into why higher intelligence was associated with higher depression rates in autism, we can make some guesses.
On the one hand, it could be that individuals with autism who have above average intelligence are more aware of the social difficulties associated with their autism diagnosis, and this awareness leads to higher rates of depression.
On the other hand, it could be that individuals with below average intelligence have difficulties communicating their symptoms, making it difficult to diagnose depression in this subgroup.
The impact of research methods
We also learned that how studies assessed depression influenced the rates of depression. Rates were highest among studies that used standardized structured interviews to assess depression, compared to studies that used less formal assessment methods.
It is possible that structured interviews may be picking up on symptoms that other assessment methods are missing. At the same time, structured interviews may bias the prevalence of depression because these interviews were not designed for people with autism.
Depression is also more common when clinicians ask the person with autism directly about their symptoms, rather than asking a caregiver.
It is possible that individuals with autism are experiencing depressive symptoms that their caregivers are missing. It is also possible that studies used a caregiver when participants were not able to report on their own symptoms (for example because of low intelligence).
Depression is more widespread in people with autism than we previously thought.
This important research will hopefully prompt clinicians to include an assessment of depression in their routine clinical practice with people with autism. This assessment will ensure that people with autism are receiving appropriate treatment.
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