Compared with the general UK population, adults with Asperger’s syndrome are much more likely to experience suicidal thoughts and plan or attempt suicide, a clinical cohort study has found.

Patients attending a specialist diagnostic clinic for adults with suspected Asperger’s syndrome were asked to complete a screening questionnaire before attending for a face-to-face diagnostic interview. They were asked whether they had ‘ever been diagnosed with depression’, whether they had ‘ever felt suicidal’, and whether they had ‘ever planned or attempted suicide’.

Asperger’s syndrome was diagnosed by an expert clinician, using the Adult Asperger Assessment and clinical judgement. Over a nine-year period, 374 adults (256 men and 118 women) were diagnosed with Asperger’s syndrome, of whom 367 completed the questionnaire. Mean age at diagnosis was 31.5 years.

A number of comparison samples were used: the 2007 survey of psychiatric morbidity in adults living in private households in England,1 and US samples of adults with medical illness,² adults with psychosis,³ and adults with comorbid ADHD and substance dependence.⁴

Of the 367 participants:

• 116 (32%) reported depression

• 243 (66%) suicidal ideation

• 27 (35%) suicidal plans/attempts

Compared with the UK population sample, participants were significantly more likely to report lifetime experience of suicidal ideation, odds ratio 9.6 (95% CI:7.6-11.9; P < 0.0001). They were also significantly more likely to report suicidal ideation than patients in the US with medical illnesses or psychosis.

Odds ratios can be misleading when the risk is high.5 These results do not mean that the lifetime experience of suicidal ideation was more than nine times higher than in the general population. The prevalence of suicidal ideation in the latter was 16.7% therefore the relative risk was 4.

Unfortunately, this study has a number of significant limitations.

The control groups were completely unmatched and only one group was from the UK. The UK household survey found that suicidal ideation was more common in younger patients, female patients and those with low incomes.¹

Therefore, in the present study, it is likely that confounding will have occurred as a result of the preponderance of young patients (two-thirds were aged < 35) and male patients, and the fact that those with Asperger’s syndrome are more likely to have low incomes.

The comparison groups did not use the same questionnaire. It is likely that different wording will have influenced the responses: compare ‘have you ever felt suicidal?’ with ‘have you ever thought of taking your life, even though you would not actually do it?’1 and ‘have you ever felt so low you thought of committing suicide?^’3

The authors acknowledge that combining suicidal plans and attempts in the same question was unsatisfactory: this meant that they could not make a comparison with previous studies.

The context in which the questionnaire was completed was different from that in the comparison groups i.e. just before a diagnostic interview rather than as part of a population survey, and this may have led to recall bias.

It is surprising that twice as many participants reported suicidal ideation as those who reported depression: the authors suggest this may reflect the difficulty that Asperger’s individuals have in articulating their emotions.

Despite these limitations, the high level of relative risk suggests that the findings of the study are likely to be valid.

There are a number of reasons why patients with Asperger’s syndrome may be at increased risk of suicide including vulnerability to anxiety and depression, social isolation, low self-esteem and impulsivity.⁶

A significant proportion of adults with Asperger’s syndrome remain undiagnosed and lack access to psychosocial interventions which may improve social interaction and life skills and thereby reduce the risk of mental illness and suicide.⁷

We should recognise the significance of a diagnosis of Asperger’s syndrome when carrying out a suicide risk assessment, and we need to be aware of our key role in identifying those with undiagnosed Asperger’s syndrome.

Dr Phillip Bland