What is mental health?

Although it might seem easy to define mental health as the absence of mental illness, most experts agree that there is more to being mentally healthy. The U.S. Surgeon General has defined mental health as "a state of successful performance of mental function, resulting in productive activities, fulfilling relationships with people, and the ability to adapt to change and to cope with adversity." The state of being mentally healthy is enviable given the advantages it affords. For example, mentally healthy adults tend to report the fewest health-related limitations of their routine activities, the fewest full or partially missed days of work, and the healthiest social functioning (for example, low helplessness, clear life goals, high resilience, and high levels of intimacy in their lives).

What is mental illness?

Mental illness refers to all of the diagnosable mental disorders. Mental disorders are characterized by abnormalities in thinking, feelings, or behaviors. Highly common, about 46% of Americans can expect to meet the formal diagnostic criteria for some form of anxiety, depressive, behavioral, thought, or substance-abuse disorder during their lifetime.

What are common types of mental illness?

Some of the most common types of mental illness include anxiety, depressive, behavioral, and substance-abuse disorders. Examples of anxiety disorders include phobias, panic disorder, generalized anxiety disorder (GAD), social anxiety disorder, and obsessive compulsive disorder (OCD). Anxiety disorders are characterized by excessive worry to the point of interfering with the sufferer's ability to function. Examples of anxiety disorders include the following:

• Phobias: involve severe, irrational fear of a thing or situation. Examples of phobias include fear of heights (acrophobia), spiders (arachnophobia), and of venturing away from home (agoraphobia).
• Social anxiety disorder is the fear of being in social situations or feeling scrutinized, like when speaking in public.
• Generalized anxiety disorder (GAD) tends to result in the person either worrying excessively about many aspects of their life (like about money, family members, the future) or having a free-floating anxiety that is otherwise hard to describe. GAD is quite common, affecting about 10% of the population.
• Panic disorder is characterized by recurring episodes of sudden, severe, debilitating anxiety (panic) attacks that are immobilizing. Those episodes usually include symptoms like racing heart beat, shortness of breath, stomach upset, and trouble thinking. In order to be diagnosed as having panic disorder, the person must also either worry about having another attack or about what the attack means (for example, wondering if the symptoms of panic indicate they are having a heart attack).

Behavioral disorders (like attention deficit hyperactivity disorder [ADHD], oppositional defiant disorder, or conduct disorder) are characterized by problems conforming to the tenets of acceptable behavior. The most common behavior disorder is ADHD; this condition includes symptoms of inattention and/or hyperactivity and impulsivity. While it used to be considered primarily a disorder of boys, it is now understood to be just as likely to occur in girls and that it can persist into adulthood in about half of children with ADHD.
Dementia, including Alzheimer's dementia, is characterized by a problem with thinking, involving both memory problems and other forms of thinking. These are also known as cognitive problems and include difficulties with language or with identifying or recognizing things despite having no medical cause for these issues such as stroke or a brain tumor.
Depressive disorders involve feelings of sadness that interfere with the individual's ability to function or, as with adjustment disorder, persist longer than most people experience in reaction to a particular life stressor. Examples of depressive disorders include the following:

• Major depression involves the sufferer feeling depressed most days and for most of each day for at least two weeks in a row. Along with sadness, the individual with major depression experiences a number of other associated symptoms, like irritability, loss of motivation or interest in activities they usually enjoy, hopelessness, and increased or decreased sleep, appetite, and/or weight. The person might also exhibit thoughts, plans, or attempts to harm themselves. Women with postpartum depression tend to experience many of the above symptoms for weeks to months after giving birth.
• Dysthymia sufferers experience depression and milder levels of the symptoms of major depression. In dysthymia, the symptoms are fairly consistent for more than two years in adults and one year in children and adolescents.
• Bipolar disorder, also called manic depression, is a mental illness that is characterized by severe mood swings, repeated episodes of depression, and at least one episode of mania in the person's lifetime. Bipolar disorder is one kind of mood disorder that afflicts more than 1% of adults in the United States, up to as many as 4 million people.

Substance use disorders, like substance abuse and substance dependence, involve the use of a substance that interferes with the social, emotional, physical, educational, or vocational functioning of the person using it. These disorders afflict millions of people and a variety of legal (for example, alcohol and inhalants like household cleaners) and/or illegal (for example, marijuana in most states, cocaine, Ecstasy, and opiates) substances may be involved.
Developmental disorders, like a learning disability, Asperger's disorder, or mental retardation, are often included in diagnostic manuals for mental disorders, but this group of conditions does not by definition mean the person involved has a problem with their mood.
It is important to understand that the list of conditions above is by no means exhaustive. This article focuses on the more common mental illnesses; illnesses like eating disorders and schizophrenia, that are less common but perhaps quite devastating to the life of the person with the condition, are omitted.

http://www.medicinenet.com/mental_health_psychology/page2.htm