One of the brain areas still maturing during adolescence is the prefrontal cortex—the part of the brain that allows people to assess situations, make sound decisions, and keep emotions and desires under control. The fact that this critical part of a teen's brain is still a work in progress puts them at increased risk for making poor decisions, such as trying drugs or continuing to take them. Introducing drugs during this period of development may cause brain changes that have profound and long-lasting consequences. Transformations Drug & Alcohol Treatment Centers
Alcoholism can also be categorized into 2 types: early-onset (biological predisposition to the disease) or late-onset (brought on by environmental or psychosocial triggers). Understanding and studying the difference between early- and late-onset alcoholism facilitate the selection of the appropriate therapy. Drugs that affect the rewarding behavior of neural activities, such as ondansetron, naltrexone, topiramate, and baclofen, have been shown to alter drinking behavior. 
For many recovering alcoholics, the mental health aspects of treatment are the most important. Improving mental health means helping patients better understand the chronic condition they are suffering from. It means equipping them with the tools they need to control their thoughts and emotions, avoid addictive triggers, and just stay away from alcohol altogether.
The signs of addiction vary from drug to drug. Some drugs take longer to produce noticeable symptoms. In some cases, the symptoms blend in with normal behaviors, making it difficult to tell that the person is addicted. Common signs of addiction include needle marks on the arms of people who inject drugs and constant nose sores on people who snort drugs.
Alcohol dependency is different for different people. Although many sufferers share things in common, their relationships with alcohol might at first seem to be nothing alike. This can make it difficult for people to identify themselves as alcohol dependent, even as drinking has an increasingly more damaging effect on their relationships, health, and enjoyment of life.
^ "Diagnostic and Statistical Manual of Mental Disorders: DSM-5 (5th edition)2014 102 Diagnostic and Statistical Manual of Mental Disorders: DSM-5 (5th edition) Washington, DC American Psychiatric Association 2013 xliv+947 pp. 9780890425541(hbck);9780890425558(pbck) £175 $199 (hbck); £45 $69 (pbck)". Reference Reviews. 28 (3): 36–37. 2014-03-11. doi:10.1108/rr-10-2013-0256. ISSN 0950-4125.
As it gradually unfolds, drug addiction causes structural changes in the brain that distort thinking and perception, specifically in areas related to behavioral control, judgment, decision-making, learning, and memory. Drug addicts suffer enormously negative life consequences as a result of their compulsive and uncontrolled drug use, but that doesn’t prevent them from returning to drugs again and again.
Stimulants, such as tobacco, cocaine or prescription amphetamines, stimulate the brain and nervous system, causing increased alertness. Depressants, such as barbiturates and benzodiazepines, slow activity in the brain and nervous system, causing relaxation. Hallucinogens, such as LSD and PCP, drastically disrupt the way the brain and nervous system communicate, causing hallucinations. Rehab: Last Week Tonight with John Oliver (HBO)