Stratified sampling is often used when one or more of the stratums in the population have a low incidence relative to the other stratums. Convenience sampling is used in exploratory research where the researcher is interested in getting an inexpensive approximation of the truth.
Sometimes symptoms of a mental health disorder appear as physical problems, such as stomach pain, back pain, headache, or other unexplained aches and pains.
Mental illness is nothing to be ashamed of. It is a medical problem, just like heart disease or diabetes. Mental illnesses are health conditions involving changes in thinking, emotion or behavior (or a combination of these). Mental illnesses are associated with distress and/or problems functioning in social, work or family activities. Mental illness is common. In a given year: