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.
Millions of Americans live with various types of mental illness and mental health problems, such as social anxiety, obsessive compulsive disorder, drug addiction, and personality disorders. Treatment options include medication and psychotherapy.
When to see a doctor. If you have any signs or symptoms of a mental illness, see your primary care provider or mental health specialist. Most mental illnesses don't improve on their own, and if untreated, a mental illness may get worse over time and cause serious problems.ental illness symptoms can affect emotions, thoughts and behaviors. Examples of signs and symptoms include: 1  Feeling sad or down. 2  Confused thinking or reduced ability to concentrate. 3  Excessive fears or worries, or extreme feelings of guilt.