"Repeated heroin use changes the physical structure and physiology of the brain, creating long-term imbalances in neuronal and hormonal systems that are not easily reversed. Studies have shown some deterioration of the brain’s white matter due to heroin use, which may affect decision-making abilities, the ability to regulate behavior, and responses to stressful situations."

I expected something more damning. Unfortunately, I feel that we don't have enough studies (incl. long-term ones) when it comes to recreational drugs.