Cannabis use may be linked to the onset and exacerbation of mania symptoms, a new study has found.
Mental health researchers from University of Warwick in the UK 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.
"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? But also, does cannabis use increase the risk of onset of mania symptoms in those without pre-existing bipolar disorder?" lead author Dr Steven Marwaha said.
The researchers looked at a number of previous studies and concluded that cannabis use preceded the onset of mania symptoms.
"The observed tendency for cannabis use to precede or coincide with rather than follow mania symptoms, and the more specific association between cannabis use and new onset manic symptoms, suggests potential causal influences from cannabis use to the development of mania. It is a significant link," said Marwaha.
Marwaha also said 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.
"However our review suggests that cannabis use is a major clinical problem occurring early in the evolving course of bipolar disorder," said Marwaha.
The research was published in the Journal of Affective Disorders.
