Instant Expert: Mental Health
When the heart breaks down, it beats irregularly or not at all. A bone can chip or snap. But when the complex network of neurons in our brain fails to function normally, the result can be a near-endless variety and combinations of mental illnesses.
It's normal to sometimes be sad, happy, anxious, confused, forgetful or fearful, but when a person's emotions, thoughts or behavior. frequently trouble them, or disrupt their lives, they may be suffering from mental illness. According to the World Health Organization (WHO), about 450 million people worldwide are affected by mental, neurological or behavioral problems at any time.
However, determining that someone has a mental illness, and which one, is one of the challenges psychiatrists face. One effort to catalogue these afflictions is the "psychiatrists' bible", the Diagnostic and Statistical Manual of Mental Disorders--the latest edition fills nearly one thousand pages and lists over 400 disorders.
Diversity of disorders
Among the best known and most common mental illnesses is depression-a prolonged, weakening sad- ness, sometimes accompanied by a feeling of hopelessness and thoughts of suicide. Seasonal affective disorder is a type of depression that affects some people in the autumn and winter and is triggered by the disappearing hours of daylight and colder temperatures. In bipolar disorder (双极性障碍), a person changes from depression to episodes of excessive enthusiasm where they are unrealistically confident in their abilities.
Personality disorders are behavior. patterns that are destructive to the person themselves or those around them. In dissociative disorders, someone experiences a sudden change in consciousness or their concept of self. In dissociative amnesia, for example, the result is a loss of part or all of their memories. Samson, the Biblical strongman, may have suffered from the earliest recorded case of antisocial personality disorder.
Anxiety disorders are characterized by powerful feelings of stress and physical signs of fear-sweating, a racing heart-due to some cue in the environment, or for no obvious reason at all. These include post-traumatic (创伤后的) stress disorder, panic disorder, obsessive compulsive disorder, anger disorders, hypochondria, social phobia, and other phobias including agoraphobia (open spaces), claustrophobia (small spaces), acrophobia (heights), and arachnophobia (spiders).
Attention-deficit hyperactivity disorder is among the most common mental illnesses diagnosed in children, affecting their ability to focus and associated with high levels of activity and impulsiveness.
Eating disorders involve an unhealthy relationship to food. A sufferer of anorexia nervosa (神经性厌食症) will strive for thinness to the point of starvation, due to a distorted perception of their bodies and dissatisfaction in their sense of control. They engage in cycles of gorging(feed greedily) themselves and then purging through vomiting or the use of some drugs. Muscle dysmorphia is sometimes thought of as a "reverse" form. of anorexia that affects bodybuilders. Sufferers constantly worry that they are too weak despite being extremely strong.
Enormous cost
Mental illnesses are quite common. As many as one in five people are thought to suffer from mental illness, at least temporarily, each year. Suicide--often the result of untreated mental illness--claims 873000 lives around the world each year. The economic costs of these conditions are also enormous and growing. According to the WHO, depression is expected to account for more lost years of healthy life than any other disease by 2030, except for HIV/AIDS.
Even so, the mentally ill face disgrace and discrimination. Studies find people are reluctant to admit they have at mental illness, to seek help, or to stick with treatment. Others are eager to reject the label of a mental

A. irregularity of heart
B. snapped bones
C. the malfunction of the neural network in brain
D. the malfunction of the brain