Anxiety is what you feel when you anticipate a threat of some kind; it can range from discomfort to dread. Someone who is very anxious most of the time--often enough to find life difficult to manage, is said to have an anxiety disorder.

Some common symptoms of anxiety include the fight-or-flight response (increased heart rate, respiration rate, and blood pressure), insomnia, a lack of appetite, excessive worry, the inability to sit still, irritability, hand wringing or fingernail biting, and phobias (irrational fears).

Coping strategies for anxiety can be healthy responses or not-so-healthy ones. In extreme cases, people may resort to other illness behaviors to reduce their anxiety. For instance, they may develop one of these additional disorders:

Obsessive-Compulsive Disorder (OCD):

Compulsive behavior, such as hand washing or checking dozens of times to see if they turned the oven off, can help reduce anxiety for some people.

Eating disorders (anorexia, bulimia, binge eating):

Strictly limiting what they eat, exercising to excess, purging behaviors, and binge eating are all unhealthy ways some people manage their anxiety.

Substance Use Disorders:

Other people try to self-medicate using alcohol or recreational or prescription drugs.

Treatment for anxiety disorder generally involves therapy with a trained psychologist or counselor. Cognitive-behavioral therapy (CBT) is believed to be especially effective for anxiety disorders. Anti-anxiety prescription drugs can be used short term, but they are not effective for long-term use. Lifestyle changes, such as time management, exercise, and meditation, can all help to reduce anxiety.

Depression is marked by prolonged feelings of sadness, helplessness, hopelessness, and exhaustion. It is not the same as feeling sad for several days because something awful has happened to you.

Some common symptoms of depression include sleep disturbances (either oversleeping or insomnia), changes in appetite resulting in weight loss or gain, apathy (lack of concern for own appearance, work or school performance), difficulty making decisions, memory problems, loss of interest in once-pleasurable activities, and thoughts of death or suicide.

As with anxiety disorder, the coping strategies that people choose for dealing with depression can be quite damaging and, in extreme cases, people may resort to other illness behaviors to reduce their depression. They may develop a substance use disorders, attempting to self-medicate their depression with alcohol or with recreational or prescription drugs. They may even attempt suicide.

For major depression, antidepressant prescription drugs are the first-line treatment. Antidepressants are effective for long-term use to regulate faulty brain biochemistry. "Talk therapy" with a trained professional is less effective than antidepressants for major depression, but it can be helpful for less severe types. For major depression that does not respond to antidepressant medications, electroconvulsive therapy (ECT, shock therapy) can be an effective treatment. In ECT, a strong electric current is sent through the skull to "reset" the brain.