Mental Disorders/epidemiology; Patient Acceptance of Health Care/psychology; Patient Acceptance of Health Care/statistics & numerical data; Students/statistics & numerical data; Adolescent; Anxiety Disorders/diagnosis; Anxiety Disorders/epidemiology; Anxiety Disorders/psychology; Comorbidity; Cross-Sectional Studies; Depressive Disorder, Major/diagnosis; Depressive Disorder, Major/epidemiology; Depressive Disorder, Major/psychology; Diagnostic and Statistical Manual of Mental Disorders; Educational Status; Female; France/epidemiology; Humans; Male; Mental Disorders/diagnosis; Mental Disorders/psychology; Prevalence; Psychiatric Status Rating Scales; Social Class; Socioeconomic Factors; Students/psychology; Substance-Related Disorders/diagnosis; Substance-Related Disorders/epidemiology; Substance-Related Disorders/psychology; Surveys and Questionnaires; Universities; White People; Young Adult