It’s cold outside, and dark. Time to toke.

Currently, 28 states allow medical marijuana for a number of conditions including postpartum depression. The stigma is slowly fading in places like California where doctors can now recommend cannabis to their patients.

The most comprehensive research review ever done on the topic found that marijuana can help battle depression, anxiety, post-traumatic stress disorder, and even addictions to alcohol and painkillers.

Scientists have found that lasting stress also depresses endocannabinoids -- neurotransmitters similar to the active ingredients in cannabis -- and that, in turn, can depress us.