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.
Some general symptoms that may suggest a mental illness include: In adults. 1  Confused thinking. 2  Long-lasting sadness or irritability. 3  Extremely high and low moods. 4  Excessive fear, worry, or anxiety. 5  Social withdrawal.