People with bipolar disorder may experience an increase in their manic or depressive symptoms if they use cannabis, a new study has found.

Bipolar disorder, previously known as manic depression, results in a person experiencing periods of elation or mania, alternating with periods of depression.

A characteristic of people in the elation state is that they are talkative, full of energy and may be involved in many plans and events. As a result, they are often unaware of the problem because they feel energetic and full of life.

However, they also experience depressive symptoms such as persistent feelings of sadness, anxiety or worthlessness, sleeping problems, poor concentration and changes in appetite.

Cannabis use among people with bipolar disorder is known to be relatively high, however research in this area is limited, so UK researchers decided to look into it further. This marked the first study to assess the use of cannabis in the context of daily life among bipolar people.

The researchers monitored people with bipolar disorder over a six-day period. Each participant filled in a diary about their emotional state, as well as their drug use.

The study found that use of the drug was linked with an increase in manic symptoms in some people, but in others, it increased depressive symptoms.

"One theory that is used to explain high levels of drug use is that people use cannabis to self-medicate their symptoms of bipolar disorder. Our findings suggest that cannabis is not being used to self-medicate small changes in symptoms within the context of daily life. However, cannabis use itself may be associated with both positive and negative emotional states.

"We need to find out whether these relationships play out in the longer term as this may have an impact on a person's course of bipolar disorder," commented lead researcher, Dr Elizabeth Tyler, of Lancaster University.

Details of these findings are published in the journal, PLOS ONE.

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