Depression is one of the most common mental illnesses in the United States, affecting more than 16 million men and women (almost 6.7 percent of the adult population) and 3.1 million adolescents.
It is a serious mental illness in which feelings of sadness, hopelessness, loss of interest, anger, frustration, or other negative emotions like irritability (especially in adolescents) last for weeks or years and interfere with daily life.
All people experience moments when they feel sad or blue, but these feelings usually pass within a couple of days and are not indicative of depression.
Depression can cause deep emotional pain both to the person experiencing it and, often, to that person’s close family and friends.
Depression is a significant public-health issue. It is the leading cause of disability in the United States for people between ages 15 and 44 and is the number one cause of injury or illness for men and women around the world. People with depression are more likely to die from suicide as well as from other illnesses, such as heart disease.
What Is Depression?
There are several different types of medically recognized depression.
The most common type of depression is called major depression, and it occurs when symptoms interfere with the enjoyment of life or with daily functions — including work, sleep, and eating habits — for at least two weeks straight.
Some people experience only one episode of major depression in their life, while others may go through numerous recurrent episodes of the illness.
In comparison, people with a condition known as persistent depressive disorder — also known as dysthymia — experience a depressed mood that lasts continuously for at least two years.
A person with dysthymia may experience episodes of major depression as well as periods of less severe symptoms.
Other common types of depression include:
Postpartum depression, in which mothers experience symptoms of major depression after giving birth. Mood impairment is much stronger, and lasts longer, than the “baby blues” — the relatively mild symptoms of depression and anxiety that many new mothers experience. Feelings of extreme sadness, anxiety, or exhaustion can make it difficult for the mother to bond with or care for her baby.
Seasonal affective disorder (SAD), in which depression occurs in during winter, and sometimes fall, and is associated with a lack of sunlight. This depression is typically accompanied by social withdrawal, increased sleep, and weight gain.
Major depression with psychotic features, in which severe depression accompanies loss of touch with reality, such as delusions (false fixed beliefs) and hallucinations (hearing and seeing things other people can’t). These psychotic features can focus on a kind of theme, such as illusions of illness or poverty.
Premenstrual dysphoric disorder, in which symptoms of depression develop a week before a woman’s period and pass after menstruation.
Some people who experience depression may have bipolar disorder — formerly called manic depression — which is characterized by moods that cycle between extreme highs (mania) and lows (depression).
How Many People Experience Depression?
In the United States, depression is one of the most common mental health disorders. And it is becoming more prevalent, especially among adolescents.
In 2016, 16.2 million adults age 18 older — almost 6.7 percent of adults — had at least one major depressive episode. (1) Additionally, 3.1 million adolescents — 19.4 percent of girls and 6.4 percent of boys — have experienced major depression. The increase in depression rates among adolescents has outpaced all other age groups.
Persistent depressive disorder affects about 1.5 percent of the adult population.
According to the NIH, women in the U.S. are significantly more likely to experience depression (8.5 percent) than men (4.8 percent).
Among adults, people between ages 18 and 25 are most at risk for depression (10.9 percent), whereas those older than 50 are at the lowest risk (4.8 percent).
When racial and ethnic factors are considered, adults who identify with two or more racial or ethnic groups show the highest rate of depression (10.5 percent).
Having one depressive episode increases your risk of having another later in life. According to a study in Psychological Medicine, more than 13 percent of people who recover from their first episode of major depression go on to have another episode within five years; 23 percent within 10 years; and 42 percent within 20 years.
Globally, depression affects more than 300 million people of all ages, according to the World Health Organization (WHO). That is the equivalent of 4.4 percent of the global population.
Depression is the leading cause of disability worldwide. Fewer than half those living with depression — and in some countries, fewer than 10 percent — receive the care they need. A number of factors prevent people from getting treatment, such as lack of trained health-care providers, social stigma, and misdiagnosis.
Different Cultures Experience Different Rates of Depression
For instance, the prevalence of depressive disorders appears to be low in Papua New Guinea (3 percent of the total population) and high in Ukraine (6.3 percent).
What Causes Depression?
There are numerous factors that can trigger the onset of depression, including bereavement, illness (such as cancer or chronic pain), social isolation or loneliness, and stressful life events (such as divorce or money difficulties). Depression can also occur spontaneously, without any obvious cause.
A person who experiences anxiety is at high risk for developing depression, and vice versa. Nearly half those who are diagnosed with anxiety are also diagnosed with depression.
Scientists don’t know exactly why some people develop depression and others avoid it. Several factors most likely contribute to the development of depression, including:
Genetics (mood disorders and suicide run in families)
Trauma or abuse at an early age, which can cause long-term changes in how the brain deals with fear and stress
Brain structure and chemistry (imaging studies have shown that the frontal lobe becomes less active when a person is depressed)
Substance abuse (approximately 30 percent of people who abuse drugs or alcohol also have depression, requiring a coordinated treatment approach)
Other medical conditions (people with sleep disturbances, cancer, chronic pain, and attention deficit hyperactivity disorder —ADHD — are more likely to develop depression)
Understanding all the complicated ways depression can manifest itself — in men, women, and, increasingly, teenagers — is the first step toward finding the right treatment for a mental illness that affects an estimated 300 million people around the world.
By Joseph Bennington-Castro Medically Reviewed by Robert Jasmer, MD
Therapist Dr. Jan Martin Dunn, PLLC, LMFT-S, LPC-S, LCDC offers Couples Counseling Dallas Individual Counseling, Couples Counseling, Family & Group Counseling.