Stress can be caused by both internal and external factors and affects the body in various ways. When the brain perceives a threat, it signals the adrenal glands to release hormones like adrenaline and cortisol that increase heart rate, blood pressure, and blood sugar levels. For adolescents, common stressors include peer pressure, relationships, schoolwork, family problems, and physical changes of puberty. Stress can lead to ineffective coping behaviors like withdrawal, substance abuse, or acting out. The most effective strategies for adolescents to manage stress are problem-focused coping, social support, meditation, exercise, humor, and emotional regulation techniques.