G-13 is one of the most powerful strains available on the market today. This highly potent, pure indica should only be used to treat depression and PTSD by patients who medicate with cannabis on a regular basis. This is due to not just the tremendous THC levels this strain contains, but also the above average THCV content, which explains why the effects come on so quickly. It is not uncommon for patients to refer to G-13 as a "heavy-hitter" for this very reason. For those who have a high THC threshold, G-13 is a great anti-depressant medication for nighttime use.