The use of cannabis as an adolescent or young adult may lead to increased ADHD symptoms at age 25.
A study from New Zealand has suggested that the use of cannabis in adolescence and young adulthood may lead to increased ADHD symptoms by age 25. The researchers followed a birth cohort of 1256 children for 25 years. The children were measured on scales for adolescent and young adult cannabis use, ADHD symptoms at age 25, childhood socioeconomic disadvantage, family adversity, childhood and early adolescent behavioral adjustment, cognitive ability, and other drug use during adolescence and young adulthood.
The results suggested that, even when one controls for variables that may also lead to adult ADHD symptoms like behavioral adjustment and cognitive ability, the use of cannabis leads to a significant increase in adult ADHD symptoms, as reported by the participants themselves.
The researchers concluded that drug use may lead to increased ADHD symptomatology, but that genetic factors and environmental effects also need to be taken into account.