Cannabis may make bipolar symptoms worse

"There are limited studies addressing the association of cannabis use and manic symptoms, which suggests this is a relatively neglected clinical issue,” says Steven Marwaha. (Credit: iStockphoto)

There’s new evidence to suggest a significant relationship between cannabis use and the onset and exacerbation of mania symptoms.

In a paper published in the Journal of Affective Disorders, mental health researchers from Warwick Medical School carried out a review of scientific literature examining the effect of cannabis use. The literature sampled 2,391 individuals who had experienced mania symptoms.

Mania symptoms are part of bipolar disorder and can include feelings of persistent elation, heightened energy and hyperactivity, and a reduced need for sleep. Mania can also make people feel angry and aggressive with extreme symptoms including becoming delusional or hearing voices.

‘A significant link’

“Previously it has been unclear whether cannabis use predates manic episodes. We wanted to answer two questions: does cannabis use lead to increased occurrence of mania symptoms or manic episodes in individuals with pre-existing bipolar disorder?” says lead author Steven Marwaha.

“But also, does cannabis use increase the risk of onset of mania symptoms in those without pre-existing bipolar disorder?”

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The researchers looked at a number of previous studies and concluded that cannabis use preceded the onset of mania symptoms.

Marwaha says “the tendency for cannabis use to precede or coincide with rather than follow mania symptoms” as well as the link between cannabis and onset of new manic symptoms suggests it’s “a significant link.”

Marwaha also says the review suggested that cannabis use significantly worsened mania symptoms in people who had previously been diagnosed with bipolar disorder.

“There are limited studies addressing the association of cannabis use and manic symptoms, which suggests this is a relatively neglected clinical issue,” adds Marwaha. “However our review suggests that cannabis use is a major clinical problem occurring early in the evolving course of bipolar disorder.

“More research is needed to consider specific pathways from cannabis use to mania and how these may be effected by genetic vulnerability and environmental risk factors.”

Source: University of Warwick