People who abuse drugs or alcohol will experience a spike in anxiety, depression, or some other type of mental disorder, and it all depends on the person’s genetic makeup.
The repeated use of a drug can put the individual in a state of psychosis which is where the symptoms of a mental illness can begin to show. Drinking any type of alcohol over an extended period of time can damage the brain and can lead to chronic depression.
Heavy drug abuse can cause a chemical imbalance in the brain, meaning that one day a person feels content and the next, not so much. With the use of Adderall, for example, an unnaturally high amount of dopamine is released in the brain putting one in a state of nirvana. However, after the drug wears off the user will feel drained, irritated, depressed.
With extended use, the dopamine receptors become damaged. This can create anxiety and depression for the individual since the brain became dependent on the drug producing the dopamine for them.