Suspiciousness may be caused by the following diseases: First, schizophrenia, which is a very serious mental illness, is prone to hallucinations, delusions, sensitivity, paranoia, behavioral disorders and other disease manifestations, and in severe cases, people around them are always targeting themselves, suspecting that someone is trying to harm them, such as poisoning their own meals. Second, personality disorders, such as paranoia patients are prone to self-centered, selfish and even always sensitive and suspicious, such as always suspecting that people around them are talking about them, suspecting that colleagues and leaders want to harm them, etc. Third, other diseases, such as alcohol dependence and Alzheimer’s disease patients may have sensitive and suspicious problems, such as suspicion of others stealing or suspicion that his wife is having an affair, and even every day will be very suspicious, tracking and monitoring his wife, the above diseases are more common.