Regular cannabis use that starts in adolescence strips away IQ, a NIDA-supported study suggests. Participants who initiated weekly cannabis use before age 18 dropped IQ points in proportion to how long they persisted in using the drug. Persistent cannabis users’ cognitive difficulties were evident to friends and family and measurable on a battery of tests.
When the goal is to avoid using alcohol and illicit substances after being released from jail, it’s who one’s friends are that counts most. Self-control is important because it helps a person have the right kind of friends.