A mental illness is a mental or emotional condition that interferes with daily functioning.
Family history, brain chemistry, life experiences, substance use, brain injuries, environment during pregnancy, and unhealthy patterns of thinking contribute to mental illnesses.
Anxiety disorders cause extreme or unrealistic fear or dread in response to situations, experiences, or objects.
Attention-deficit hyperactivity disorder (ADHD) makes it difficult to pay attention or control behavior. Those with obsessive-compulsive disorder (OCD) experience constant and obsessive thoughts, feelings, or behaviors.
People with mood disorders such as major depressive disorder, seasonal affective disorder (SAD), and bipolar disorder experience extreme changes in the way they feel.
People with behavioral disorders like oppositional defiant disorder (ODD) or conduct disorder show patterns of inappropriate behavior.