By Professor Guy Goodwin

Bipolar disorder is a co-morbidity disorder. That means at least two-thirds of patients with a bipolar disorder also have another psychiatric condition. The most common are anxiety, substance use and impulse control disorders. Co-morbidity can obscure the diagnosis of bipolarity, worsen bipolar symptoms and tends to make treatment approaches to bipolar disorder itself less effective. 

Co-morbidity may occur because mood disorders share a common cause or causes: with anxiety, for example. We all know how we experience anxiety personally – but if you ask a broad sample of the population, anxiety proneness varies a lot. High anxiety is expressed as a tendency to anxious worry. It is a personality trait which is usually called neuroticism. Neuroticism runs in families and is observed as a temperament in young children. It tends to be higher on average in women than men, and there is a substantially greater number of women than men with really high neuroticism. Anxiety is so prevalent among bipolar patients that it is hard to justify calling it a separate condition, except that it may require a particular approach to treatment, additional to the medication that prevents manic episodes for example. Bipolar anxiety seems to be associated quite commonly with vivid imagery. Imagery is literally seeing with the mind’s eye. We are all familiar with anxious thoughts, but anxiety provoking images are more unusual. They are best described in relation to traumatic events which can be recalled very violently with a lot of distressing emotion. The anxious imagery of bipolar disorder may be less amenable to conventional anxiety management techniques. Research is ongoing into better ways of approaching it, informed by experience with trauma patients. 

Other co-morbidities may be best seen as consequences of anxiety and mood instability. Alcohol use often starts as a remedy for social anxiety. The addictive qualities of alcohol and other drugs may be accelerated by how bipolar disorder shapes emotional responses. In young people with hypomanic experience but not fully formed bipolar disorder, alcohol has less of an impact on subjective mood but is associated with greater expectation of positive effects. That is a risky combination because it could drive higher levels of alcohol consumption, which is exactly what we see in as many as 30% of patients with severe bipolar disorder. 

Impulse control disorders are closely related to the addictions. Gambling is the most important example. As many as 1 in 10 patients with bipolar disorder gamble excessively. Gambling becomes a habit in a similar way to drinking alcohol or taking drugs. Impulsive decision making is an obvious feature of mania. However, a slightly greater impulsiveness is also present in bipolar patients between episodes. Impulsive decision-making sounds like fast decision making. In fact impulsive people make decisions quite slowly, but badly. In other words, the unconscious processes that shape their actions fail to weigh risks and rewards optimally. Impulsivity is also a prominent feature of borderline personality and ADHD.

Bipolar patients are also more likely to smoke and have trouble quitting smoking. While it seems logical again to assume that bipolarity causes addiction rather than vice versa, there is very interesting new data that suggests this may not be correct for smoking. The hypothesis is that smoking itself may contribute to the onset of bipolar disorder. This is an additional reason for young people not to smoke or vape but it obviously raises intriguing questions such as whether nicotine itself is potentially responsible. This needs more work.

Finally, a range of physical diseases appear to be co-morbid with bipolar disorder. A survey of the bipolar disorder research network, which is strongly linked with Bipolar UK, showed that asthma, Type II diabetes, high blood pressure, heart disease and kidney disease are the common conditions that occur more often in bipolar patients. Whether the links are largely secondary to lifestyle choices (smoking, being overweight) or more fundamentally linked to bipolar disorder is uncertain. Either way, it is an important reason to take the physical health of bipolar patients extra seriously.

In conclusion, co-morbidity really matters in bipolar disorder. A good assessment will always take co-morbid mental and physical disorder into account when advising patients and will include their management in an effective treatment plan. The quality of the care you receive as a bipolar patient should be judged on that basis.