Heavy Cannabis Use in Teens causes IQ Decline
The Dunedin Longitudinal Study, an ongoing multi-factor survey of 1,037 New Zealanders who were monitored from birth, provided the data that the research team used. Currently, there is around 40 years' worth of data from the survey, and over the years, participants have been periodically assessed for IQ and other neurological indices.
The study's heaviest and most consistent teenage users had an average drop in IQ of 8 points from childhood to adulthood when the respondent's IQs were evaluated at age 38. During this time, non-users IQs rose by about one point. The IQ of light cannabis users continued to drop by a few points. Even after participants stopped using marijuana, the decline in mental sharpness appeared to be permanent. Consistent smokers who started as adults didn't appear to suffer from this IQ drop.
Read more about the research - https://scitechdaily.com/heavy-teenage-cannabis-use-leads-to-drop-in-iq/