Smoking cannabis can bring on symptoms of mania, new research warns.

Researchers found there is a 'significant link' between marijuana use and mania, which can range from hyperactivity and difficulty sleeping to aggression, becoming delusional and hearing voices.

The study of more than 2,000 people is especially alarming for teenagers who indulge in the habit.

Lead researcher Dr Steven Marwaha, of Warwick University, said: 'Cannabis is the most prevalent drug used by the under-18s.

'During this critical period of development, services should be especially aware of and responsive to the problems cannabis use can cause for adolescent populations.'

There is a 'significant link' between marijuana use and mania, resarchers say. This can range from hyperactivity and difficulty sleeping to aggression, becoming delusional and hearing voices

The study, published in the Journal of Affective Disorders, examined the effect of cannabis on individuals who had experienced mania.

This can include feelings of persistent elation, heightened energy, 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.

Dr Marwaha said: '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?'

He found cannabis use tended to precede or coincide with episodes of mania.

There was a strong association with new symptoms of mania - suggesting these are caused by marijuana use.

'It's a significant link,' Dr Marwaha said.

The study also found cannabis significantly worsened mania symptoms in people who had previously been diagnosed with bipolar disorder.

Dr Marwaha said: '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 cannabis use is a major clinical problem occurring early in the evolving course of bipolar disorder.

The findings add to a body of evidence that cannabis may increase rates of mental health problems including depression, anxiety, psychosis and schizophrenia

'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.'

The findings add to a body of previous studies that have linked cannabis to increased rates of mental health problems including depression, anxiety, psychosis and schizophrenia.

However, a study published this month found marijuana could be used to treat the depression that results from long term stress.

Researchers said molecules present in cannabis could help relieve the depression associated with chronic stress.

Endocannabinoids are naturally produced chemical compounds in the brain that affect motor control, cognition, emotions and behaviour.

Researchers found long term stress reduced the production of endocannabinoids in brains, leading to depression.

Endocannabinoids are similar to the chemicals found in marijuana, and its active ingredient, delta-9-tetrahydrocannabinol (THC).