Alcohol is unhealthy because it is addictive.

Alcohol triggers endorphin and dopamine chemical releases in the brain, which creates feelings of pleasure and rewards us for drinking. As one drinks more, their brain chemistry is altered, making them require more and more alcohol to achieve the same feeling. Eventually they become physically dependent on it, and many people become psychologically dependent as well, using alcohol to escape stress or depression. When one becomes addicted to alcohol (also known as alcoholism) it leads to reliance on it to the point where they can not achieve feelings of happiness or enjoyment without alcohol. It can lead to dangerous and unpleasant withdrawals when they stop drinking, which can lead to permanent health issues. Alcoholism can take one away from their lives and families by leading them to become depressed, angry, or violent.

P[1] Drinking can lead to alcoholism. P[2] Alcoholism is unhealthy.