A new study carried out by British scientists has found further evidence supporting the absence of a connection between mental decline in later life from previous drug use.
I’m not too surprised to be honest… Cannabis was shown to be the most commonly used illicit drug by the 9000 participants in this study. People were surveyed at 42 years of age and then had their cognitive abilities tested 8 years later at age 50. 12 illicit drugs were included in the study comprising substances like cocaine, LSD, psilocybin mushrooms, amphetamines and ecstasy.
The authors of the study state these findings and implications in the abstract that:
At the population level, it does not appear that current illicit drug use is associated with impaired cognitive functioning in early middle age. However, the authors cannot exclude the possibility that some individuals and groups, such as those with heavier or more prolonged use, could be harmed.
However, the authors cannot exclude the possibility that some individuals and groups, such as those with heavier or more prolonged use, could be harmed.
Although, aforementioned substances such as cannabis and cocaine have short term effects on ones cognitive abilities if used periodically, this study is further evidence for ones mental capacities returning to normal soon after use has stopped.
That said, it would be best to look at longer studies from earlier ages to really clarify things. As raised in one of the below comments by Ian, why would you expect to see a difference between the ages of 42 and 50. More interesting would be examining different degrees of usage of these drugs in much younger people, from their teens, through their adult life in order to examine long term effects of drug usage of cognitive abilities. Use at a younger age is probably much more detrimental to the mind, when it is still developing, than say at at 42 when it has long since matured.
More info here