There was no scientific evidence for this ? until now.

An estimated 166 million adults partook of cannabis in 2006, with use highest in the United States, Australia and New Zealand. Cannabis was already known to be effective in the treatment of such conditions as post-traumatic stress disorder (PTSD), chronic pain, epilepsy, multiple sclerosis, glaucoma and nausea from chemotherapy. While many people are certain that cannabis is good for depression, there was no scientific evidence for this – until now.

A study by the Research Institute on Addictions that was published in the autumn edition of the Journal of Neuroscience has shown that cannabis reduces the symptoms of depression and possibly also chronic stress. Scientists at the Institute, part of New York’s University of Buffalo, discovered that chemical compounds known as cannabinoids could help tackle depression. These are the compounds that are activated by the brain’s THC receptors.

Researchers examined the effects of chronic stress upon rats: when exposed to unending stress, their brains produced less endocannabinoids – the chemicals behind cognition, emotion, relaxation and appetite. The senior scientist, Samir Haj-Dahmane PhD, remarked that “depression-like behaviour” was then observed. The endocannabinoids produced by the body are similar to those contained in cannabis. Cannabis-derived cannabinoids were delivered to the rats, restoring endocannabinoid levels.

23 US states and the District of Columbia permit the usage of cannabis for medical reasons. Haj-Dahmane cautioned that research of rats was “a long way to go” from proving effects on humans in terms of treatment of depression, but added that PTSD sufferers had reported relief after toking. While some strains of cannabis lessen depression, others cause anxiety, including paranoia. One person blogged that Blue Hawai’ian made them “feel really weepy and crave a Peach Pleasure Jamba Juice.” Past research has indicated that heavy cannabis users are at a greater risk of depression, although some studies have contradicted this: for instance, a 2013 study published in the American Journal of Public Health found that the suicide rate dropped in states that had legalised marijuana.

A study where 80,000 men aged 45 to 69 years old were examined for 11 years that was published in the journal, Urology, found male pot smokers to be 45 percent less likely to develop bladder cancer. A 2009 study by Brown University that examined 1,000 people found that moderate long-term use of marijuana was associated with a lesser risk of head and neck cancers. A number of studies including one detailed in the journal, Annals of the American Thoracic Society, showed that, in contrast to tobacco, joint-smoking does not increase the risk of lung cancer and might even have a protective effect. In 2006, the Economist reported that if cannabis had only just been discovered, it would be hailed as a medical breakthrough.