Although the actual statistics vary from study to study, it is generally agreed that those people who have a diagnosed mental illness are at greater risk for meeting criteria for a substance use disorder and vice versa. Do these types of illnesses, mental illness and addiction, somehow travel together or are other factors at work? In particular, what is the relationship between alcohol dependence and a major depressive disorder?
It is important to understand how alcohol affects the brain. Alcohol functions as a central nervous system depressant. As a central nervous system depressant, alcohol makes it more difficult for brain cells to “talk” to one another. The brain is the body’s “command center”. If the cells in the brain have difficulty communicating, it affects a wide variety of functions. Motor coordination is impaired and reflexes are slowed. Breathing can become slower and shallower. Heart rate slows down. Thought processes are dulled and judgment is impaired. Pain is not felt as acutely. Vision is impaired, as is speech. The severity of these impairments depends upon how much a person drinks, over what period of time the drinking occurred, the person’s weight and gender, whether the person was eating or was drinking on an empty stomach, and so on. However, in general, the more alcohol one consumes, the more pronounced the effects. In severe cases, where large amounts of alcohol are consumed, the central nervous system can become so depressed that a person can pass out, slip into a coma or even die of alcohol poisoning.
So what does this have to do with depression, you ask? Actually, quite a lot. First, alcohol directly affects mood. If a person drinks alcohol regularly and in large amounts, this can directly lead the brain to interpret the person’s mood as “depressed”. Additionally, alcohol can affect mood indirectly in a number of ways. When drinking, people may do things they later regret or feel guilty about. Heavy and regular alcohol use increases the risk for legal problems, family problems, social problems and employment problems, all of which can affect mood. Alcohol use can also lead to physical health problems which can affect mood in a variety of ways.