Mental disorders
Alcohol worsens the course of mental disorders: depression, bipolar disorder, schizophrenia.
Alcohol acts as an antidepressant interfering with the activity of brain neurotransmitters. This results in the problems with concentration and emotional control.
People diagnosed with pre-existing disorders are often recommended to quit alcohol and other psychoactive substances which have adverse effects on the treatment.
Memory
People who drink a lot usually don’t eat enough. This can lead to thiamine (B1) deficit that in turn can cause Wernicke-Korsakoff syndrome (type of dementia).
Good news: vitamin supplements and total alcohol abstinence may reverse symptoms of Wernicke-Korsakoff syndrome within the first 2 years after stopping drinking.
Bad news: higher amount of alcohol consumed per week is associated with increased odds of hippocampal degeneration (the area linked to memory).

Changes in the neurobiological brain structures
The alcohol addiction leads to the changes in the basal ganglia and the prefrontal lobe as well as to hyperactivation of brain stress systems.
The prefrontal lobe is responsible for executive functions: go and stop systems. In case of addiction the go system becomes more active and the stop system is inhibited.
Physical injuries
Alcohol is a traumatic brain injury risk factor. In the state of intoxication, a person falls down more often, gets into car accidents and fights. Severe brain injuries can be fatal as the brain controls breathing and blood pressure.