A disease with certain characteristic signs and symptoms that interferes with the ability to work, sleep, eat, and enjoy once pleasurable activities.
The characteristic signs and symptoms of major depression include loss of interest in activities that were once interesting or enjoyable, including sex; loss of appetite (anorexia) with weight loss or overeating with weight gain; loss of emotional expression (flat affect); a persistently sad, anxious or empty mood; feelings of hopelessness, pessimism, guilt, worthlessness, or helplessness; social withdrawal; unusual fatigue, low energy level, a feeling of being slowed down; sleep disturbance with insomnia, early-morning awakening, or oversleeping; trouble concentrating, remembering, or making decisions; unusual restlessness or irritability; persistent physical problems such as headaches, digestive disorders, or chronic pain that do not respond to treatment; thoughts of death or suicide or suicide attempts. Alcohol or drug abuse may be signs of depression.
Disabling episodes of major depression can occur once or a number of times in a lifetime.
For more information, see Depression.
- Major gene
A gene that is necessary and sufficient by itself to cause a condition. For example, the APC gene is a major gene for colorectal cancer.
- Major histocompatibility complex
Abbreviated MHC. A cluster of genes located on chromosome 6 concerned with antigen production and critical to the success of transplantation. The MHC includes the human leukocyte antigen (HLA) genes.
Poor intestinal absorption of nutrients. Malabsorption can occur from diseases that injure the bowels, such as Crohn’s disease, Whipple’s disease, celiac disease, and many others.
Softening. For example, osteomalacia is softening of bone, usually due to deficiency of calcium and vitamin D.
A vague feeling of discomfort, one that cannot be pinned down but is often sensed as ‘just not right.’