According to the Critical Thinking Box on Smoking and Psychological

According to the Critical Thinking box on smoking and psychological disorders, what is one possible explanation for the fact that people with psychological disorders have a much higher rate of smoking than people who do not have a psychological disorder?

A) People with a psychological disorder may tend to use cigarettes as a form of self-medication.
B) People who smoke heavily develop psychological disorders because the drug nicotine in cigarettes is a main cause of mental illness.
C) People with a psychological disorder smoke heavily because nicotine decreases the production of dopamine and inhibits activity in multiple brain structures involved in producing rewarding sensation.
D) Heavy cigarette smoking causes severe psychological disorders, and the development of psychological disorders in turn causes people to smoke even more heavily.