Sociological approaches to psychological well-being are fundamentally different. The distinctive emphasis of sociological approaches is on how processes such as life events, social conditions, social roles, social structures, and cultural systems of meaning affect states of mind. Many sociologists study how social conditions affect levels of mental health. Most research that takes place in clinical settings examines particular types of mental illnesses, such as schizophrenia, bipolar disorder, major depression, and obsessive-compulsive disorder. Emile Durkheim's study, Suicide, is generally regarded as the first explicitly sociological study of mental health. Contemporary studies in the sociology of mental health confirm the importance of social integration as a fundamental cause of well-being. Social inequality relates not only to economic and work conditions but is also an aspect of all social institutions. Birth cohorts are another social influence that shapes mental health. Generational factors also affect general levels of well-being and distress.