MedGen

Depression (also known as major depression or major depressive disorder) is a psychiatric disorder that affects mood, behavior, and overall health. It causes prolonged feelings of sadness, emptiness, or hopelessness, and a loss of interest in activities that were once enjoyed. People with depression may also have changes in appetite (leading to overeating or not eating enough), changes in sleeping patterns (sleeping too much or not being able to sleep), loss of energy, and difficulty concentrating. Although depression is considered primarily a mental health disorder, it can also have physical features including headaches, other unexplained aches and pains, unusually slow or fast movements, and digestive problems. To be diagnosed with depression, an individual must have signs and symptoms nearly every day for at least 2 weeks. However, the features of this condition vary widely.

Depression most commonly begins in late adolescence or early adulthood, although it can appear at any age. If untreated, episodes of depression can last for weeks, months, or years, and can go away and come back (recur). Affected individuals may have difficulty functioning in their daily lives, including at school or work. People with depression have a higher risk of substance abuse problems and dying by suicide than the general population.

Several health conditions are closely related to depression or have depression as a characteristic feature. These include dysthymia (which has long-lasting signs and symptoms that are similar to, but not as severe as, those of depression), perinatal or postpartum depression (which occurs around or following the birth of a child), seasonal affective disorder (which is triggered by the changing of the seasons), bipolar disorder (which can include both "highs," or manic episodes, and depressive episodes), and generalized anxiety disorder. In people with schizoaffective disorder, depression or another mood disorder occurs together with features of schizophrenia (a brain disorder that affects a person's thinking, sense of self, and perceptions). [from MedlinePlus Genetics]

Attention deficit-hyperactivity disorder (ADHD) is the most common childhood-onset behavioral disorder, affecting approximately 5 to 10% of children and adolescents (Wolraich et al., 1996). In this condition, persistent inattention and/or hyperactive-impulsive behavior results in impaired social and/or academic functioning. Boys are affected about 8 times more frequently than girls (Zametkin et al., 1990). Genetic Heterogeneity of Attention Deficit-Hyperactivity Disorder Susceptibility to ADHD7 (607478) may be conferred by variation in the TPH2 gene (607478) on chromosome 12q21. ADHD8 (619957) is caused by mutation in the CDH2 gene (114020) on chromosome 18q12. Several loci for susceptibility to ADHD have been mapped, including ADHD1 (608903) on chromosome 16p13, ADHD2 (608904) on chromosome 17p11, ADHD3 (608905) on chromosome 6q12, ADHD4 (608906) on chromosome 5p13, ADHD5 (612311) on 2q21.1, and ADHD6 (612312) on 13q12.11. Also see MOLECULAR GENETICS. [from OMIM]

Attention-deficit/hyperactivity disorder (ADHD) is a behavioral disorder that typically begins in childhood and is characterized by a short attention span (inattention), an inability to be calm and stay still (hyperactivity), and poor impulse control (impulsivity). Some people with ADHD have problems with only inattention or with hyperactivity and impulsivity, but most have problems related to all three features.

In people with ADHD, the characteristic behaviors are frequent and severe enough to interfere with the activities of daily living such as school, work, and relationships with others. Because of an inability to stay focused on tasks, people with inattention may be easily distracted, forgetful, avoid tasks that require sustained attention, have difficulty organizing tasks, or frequently lose items.

Hyperactivity is usually shown by frequent movement. Individuals with this feature often fidget or tap their foot when seated, leave their seat when it is inappropriate to do so (such as in the classroom), or talk a lot and interrupt others.

Impulsivity can result in hasty actions without thought for the consequences. Individuals with poor impulse control may have difficulty waiting for their turn, deferring to others, or considering their actions before acting.

More than two-thirds of all individuals with ADHD have additional conditions, including insomnia, mood or anxiety disorders, learning disorders, or substance use disorders. Affected individuals may also have autism spectrum disorder, which is characterized by impaired communication and social interaction, or Tourette syndrome, which is a disorder characterized by repetitive and involuntary movements or noises called tics.

In most affected individuals, ADHD continues throughout life, but in about one-third of individuals, signs and symptoms of ADHD go away by adulthood. [from MedlinePlus Genetics]