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Patients with bipolar disorder have high rates of medical illness, which often exceeds the levels observed in patients with unipolar depression, show results of a UK-based study.

“This comorbidity needs to be taken into account by services in order to improve outcomes for patients with bipolar disorder and also in research investigating the aetiology of affective disorder where shared biological pathways may play a role”, say study authors Nick Craddock (Cardiff University) et al.

Craddock and team interviewed 1720 patients (median age 47 years, 70% women) with bipolar disorder about their lifetime history of 20 common medical illnesses, and compared the rates of each illness with those observed in previously described recurrent unipolar depression (n=1737) and control (n=1340) groups.

In line with previous research, the most prevalent medical conditions in both the bipolar and unipolar groups were migraine headache (23.7 and 21.9%, respectively), asthma (19.2 and 13.1%), elevated lipids (19.2 and 9.7%), hypertension (15.0 and 16.8%), thyroid disease (12.9 and 8.2%) and osteoarthritis (10.8 and 10.9%).

There were significant differences in comorbid illness prevalence among the three groups for all but one (Type 1 diabetes) of the conditions investigated. After adjustment for multiple testing, these differences remained significant for asthma, Type 2 diabetes, elevated lipids, epilepsy, gastric ulcers, hypertension, kidney disease, multiple sclerosis, osteoarthritis and thyroid disease, with the highest rates generally observed among the patients with bipolar disorder.

To investigate whether a greater burden of medical illness is associated with a more severe bipolar illness course, the team compared patients who had a history of three or more medical illnesses (n=202) with those with no medical illnesses (n=440).

They found that a high medical illness burden was significantly associated with a history of anxiety disorder (odds ratio [OR]=2.76), rapid cycling mood episodes (OR=2.25), suicide attempts (OR=2.39) and mood episodes with a typically acute onset (OR=2.56).

However, contrary to previous reports, there were no significant differences between the bipolar group with no history of medical illness and those with a high burden of medical illness in the rates of alcohol misuse or smoking.

“Although this finding requires further investigation it suggests that, at least in our bipolar sample, smoking and alcohol misuse may not be the most significant factors influencing susceptibility to medical illness burden”, Craddock et al remark.

Writing in The British Journal of Psychiatry, the authors conclude that “[k]nowing which medical illnesses are likely to coexist with a mood disorder may help to improve diagnostics and management and therefore clinical and social care for patients.”

They add that greater collaboration between mental health and other professionals offers the strongest chance of better outcomes for individuals with both mental health and physical conditions.

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Addtional Reporting By: Munreporter Publications.