There are three interrelated factors that may cause mental illness. These are the biological or physical factors, psychological factors, and socio-cultural factors.
The BIOLOGICAL FACTORS are the imbalances of the neuro-chemicals in the brain called neurotransmitters. These neurotransmitters aid the brain nerve cells communicate with each other. If these chemicals are not in balance or are not working properly, messages from the senses or organs may not make it through the brain correctly, leading to symptoms of mental illness. Moreover, the presence of injuries and defects in the brain may also cause mental illness. These are called the physical factors.