Why do mental illness and substance abuse disorders so often occur together? [Featured Partner]



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As many as 50% of drug addicts and 40% of alcoholics have at least one mental illness, and up to 30% of people who have a mental illness abuse substances. But why do mental illness and substance abuse problems so frequently occur together? While substance abuse can make mental illness symptoms worse or even trigger the onset of symptoms in people who are already susceptible to them, it’s not as simple as saying that drug and alcohol abuse cause mental illness.

Many people with mental illness symptoms abuse drugs and alcohol to self-medicate, often because they fear the stigma of admitting to mental illness problems, or because they hope the symptoms will go away on their own. But without treatment, mental illness symptoms typically get worse, and regular substance abuse can all too easily develop into full-blown addiction. Some evidence suggests that brain changes early in life may contribute to the development of comorbid substance abuse disorders and mental illness.


Could brain abnormalities cause dual diagnosis disorders?

According to research published in the journal Behavioral Neuroscience in December 2007, dual diagnosis disorders — substance abuse and mental health disorders that occur together — could be the result of changes to the amygdala that happen early in life. The amygdala is the part of the brain responsible for emotions, including fear and anxiety. Researchers from Indiana University compared the drug-related behavior and moods of two groups of adult rats. The researchers surgically injured the amygdalas of one group of rats while they were still infants. Those of the other group were left uninjured, although the researchers did perform a false surgery on the rats in order to control for the possibility that the procedure itself may have traumatized the injured group.

Those rats with the injured brains lacked the normal responsiveness to threatening or potentially threatening stimuli when they grew up. They were drawn to novel situations and showed less fear in unfamiliar surroundings, like an elevated maze. They failed to react normally to the scent of predators, continuing to socialize instead of acting self-protectively.

The brain-injured rats were also more sensitive to the effects of cocaine, and displayed drug-related changes in behavior more quickly than the non-injured rats. They appeared to become addicted more easily than their normal counterparts. The researchers concluded that the injury to the amygdala both made them more sensitive to the effects of drugs and impaired normal fear-related behaviors.

Lead study author Andrew Chambers MD believes that underlying brain problems may make it both more likely for people with mental illness to become addicted to drugs and harder for them to respond to treatment. While injury to the amygdala sustained early in life may make a person more susceptible to dual diagnosis disorders later on, environmental and genetic factors may have a similar effect on brain function.


Substance abuse and the physiology of mental illness

The same neurotransmitters, neural pathways and processes are implicated in both mental illness and addiction. Both substance abuse and schizophrenia, for example, cause an increase in dopamine in the brain. Alcoholism and mood disorders both affect serotonin levels. People with mental illnesses like schizophrenia have the same problems with pleasure and reward perception as people addicted to cocaine. Some people, like those who possess a specific variant of the catechol-o-methyltransferase gene, are more likely to develop schizophrenia as a result of regular marijuana use.

Not only can abusing substances trigger the onset of mental illness symptoms that are not yet present, it can also make existing symptoms worse. Many people abuse drugs and alcohol in an attempt to self-medicate for feelings of depression, anxiety or worse. In almost every case, substance abuse only further distorts brain chemistry and exacerbates symptoms.


Treating concurrent substance abuse and mental health disorders

In those with concurrent substance abuse and mental health disorders, treatment for mood disorders or other mental disorders must occur simultaneously with addiction treatment. It’s often difficult to tell when addiction and mental illness are occurring in the same patient, since the symptoms of a substance abuse disorder can often mimic those of a mental disorder. If mental health symptoms persist after drug and alcohol use is stopped, dual diagnosis treatment will probably be necessary.

Without treatment for both mental illness symptoms and addiction, relapse is much more difficult to avoid, since untreated mental illness symptoms can drive many recovering addicts back into substance abuse. Counseling and lifestyle changes may be necessary, and psychiatric medications may also be needed. It’s important for dual diagnosis patients to understand that using psychiatric medications to treat a mental illness is not the same as abusing substances.

Mental illness symptoms and substance abuse disorders often occur together, and the relationship between them is complex. Treatment will need to address both the mental illness and the substance abuse disorder. While dual diagnosis treatment is difficult, recovery is far from impossible. With the right kind of help, many people suffering from concurrent mental illness and addiction go on to lead productive, happy lives.