The brain’s frontal lobe, responsible for logical thinking, is not fully developed until about the age of 25, which means that younger people are more prone to risk-taking behavior. Thus, it would seem counterintuitive to think that a mature brain would contribute to substance abuse or mental problems.
But a clue to the contrary may be found in this account by Mental Health Daily: “The brain’s reward system tends to reach a high level of activation during puberty, then gradually drifts back to normal activation when a person reaches roughly the age of 25.”
My theory is that absent that “high level of activation,” the person at brain maturity might feel a sense of stagnation and get less of a high from the emotional drives that propelled the youthful brain. Thus, a person who already has a substance abuse problem might double down on their use of alcohol or other drugs in an attempt to recapture the excitement of the young risk-taking brain. And the deficit of emotional highs may have contributed to Kurt Cobain’s depression.
Of course, one should never discount personal responsibility. If you pursue a life of immediate gratification, there may be a deadly price to pay.