The cognitive process most clearly affected by cannabis is short-term memory. This usually disappears as soon as one is no longer affected. Some other short-term effects may include, immediate changes in thoughts, perceptions and information processing.
So, what about long-term effects? There’s no convincing evidence even heavy, long-term cannabis use by adults permanently impairs memory or other cognitive functions. Some studies have shown heavy cannabis use starting in the early teens has an impact on the brain. Other studies have shown no impact but what is clear is that more research is needed.
It is strongly recommended teens not use cannabis. The teenage brain is still developing and, in particular, the part of the brain that controls emotional development can be sensitive. That is one reason legalising and regulating the cannabis market to keep it out of the hands of children is so important.