Key Findings: The majority of middle school students consider themselves to be in good health (nearly 9 out of 10 students) and report a positive outlook on life (more than 8 out of 10 students). Despite good health and a positive outlook on life, one-third of 8th and 9th graders exhibit moderate or high levels of depression, and 4 out of 10 students exhibit a syndrome of complaints (somatic and/or psychological). Girls perceive themselves to be in poorer physical and psychological health than boys (lower perceived health, less positive outlook on life, higher prevalence of symptom syndrome, and higher levels of depression). Girls’ mental health follows a negative trend between 6th and 9th grade (declining perceived health and positive outlook on life), while boys’ mental health remains stable. Over the 2010–2014 period, a positive outlook on life decreased among girls, and symptom clusters increased for both genders.