How do people get Psychosis?
Psychosis can be induced either socially (environmental factors), abuse of drugs, and genetically.
There are research and experiments that even twins who are raised apart, when one of them
ABUSE OF DRUG:
The most common types of drugs are cannabinoids, opioids, stimulants, club drugs, dissociative drugs, hallucinogens, and some compounds. Among those, cannabinoids, stimulants, and dissociative drugs are known to succeed psychosis.
Stress is also known to cause psychosis in different people. Stress is a state of mental or emotional strain or tension resulting from adverse or very demanding circumstances, whereas stressors are the factors that causes stress.
It is a specific response by the body to a stimulus, as fear or pain, that disturbs or interferes with the normal physiological equilibrium of an organism. But when any of the stressors (an activity, event, or other stimulus that causes stress) is constantly disturbing you, then that's the time your body is not in its normal physiological balance. Extreme measures when not treated properly may lead to psychosis.
Hope that helps. :-)