Prevalence of psychiatric morbidity in a difficult asthma population: relationship to asthma outcome

Psychiatric morbidity appears common in fatal and near-fatal asthma and may be a factor in difficult to control asthmatic subjects. We examined the prevalence of psychiatric morbidity (using psychiatric interview) in a cohort of sequentially referred poorly controlled asthmatics and related this to (a) asthma outcome (b) assessing chest physician opinion and (c) Hospital Anxiety Depression Scale (HADS).

Patients were evaluated using a systematic evaluation protocol to identify and manage all co-morbidity. Psychiatric assessment was performed by experienced liaison psychiatrists and ICD10 diagnosis and treatment programme assigned. Subjects completed HADS at presentation and follow-up. Asthma was managed according to BTS/SIGN Guidelines.

Of 65 subjects who attended for psychiatric interview, 32 (49%) had an ICD10 diagnosis, (6 (9%) previously identified) with depression most common (59%). Physician assessment had poor discrimination for psychiatric illness. Anxiety scores (13.4+/-0.8 vs. 8.5+/-0.7) and depression scores (10.2+/-0.7 vs. 4.8+/-0.5) scores were significantly higher in subjects with ICD10 diagnosis (P<0.001), who were also more likely to be current smokers (P<0.01). HADS had a poor positive predictive value for psychiatric illness but a good negative predictive value for depression. There was no relationship between ICD10 diagnosis and asthma outcome. Subjects identified as therapy-resistant asthma after systematic evaluation, had significantly lower depression scores after treatment (P<0.05).

In difficult asthmatics, there is a high prevalence of undiagnosed psychiatric morbidity, with depression being particularly prevalent. A simple screening questionnaire such as HADS, has a high false positive rate when compared to psychiatric interview, but may be useful in excluding depressive illness. There appears to be little association between identification and management of co-existent psychiatry morbidity and asthma outcome.