Depression Causes & Effects

Learn about depression

Major depressive disorder is a mental health condition that is characterized by feelings of profound sadness and hopelessness that are severe enough to disrupt a person’s life. According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, a diagnosis of a major depressive episode is contingent upon at least five of the following symptoms being present every day or nearly every day during a two-week period:

• Depressed mood most of the day
• Markedly diminished interest or pleasure in all or most activities
• Significant change in appetite and/or weight
• Insomnia or hypersomnia
• Psychomotor agitation
• Fatigue or lack of energy
• Sense of worthlessness or inappropriate guilt
• Indecisiveness or diminished ability to concentrate
• Recurrent thoughts of death

If these symptoms are not attributable to the effects of a substance or other medical condition, and if they cause clinically significant distress or impairment in a person’s social, occupational, or other areas of functioning, then the criteria for a major depressive episode have been met.

To a non-clinician, a major depressive episode may look like a period of being “down in the dumps.” But while virtually everyone will go through brief episodes of feeling less-than-enthusiastic with the world and their place in it, individuals who are suffering from major depression experience an overwhelming set of symptoms that can render them incapable of meeting the daily responsibilities of work, school, personal relationships, and other essential components of a healthy life.

The good news is that major depression is a treatable condition that responds well to therapy, medication, or a combination of the two. Unfortunately, many people who struggle with major depression do not get the help that they need. In many cases, individuals who fail to receive effective professional care for their major depression will turn to substance abuse in a misguided attempt to self-medicate their symptoms, which often has the effect of exacerbating the depression while inflicting additional damage on the afflicted individual’s physical, mental, and socioeconomic wellbeing.

Depression statistics

According to the National Institute of Mental Health, about 15.7 million adults (or about 6.7 percent of the 18-and-above demographic) in the United States experienced at least one major depressive episode in 2013 (the most recent year for which such statistics are available).

A study that was published by the National Center for Biotechnology Information (NCBI) indicates that, among senior adults, about half of those who experience depression had prior depressive episodes before reaching age 60, while the other half experienced their first depressive episode after their 60^th birthday. The World Health Organization (WHO) estimates that major depression accounts for 3.7 percent of all years lost to illness, disability, or premature death in the United States.

Causes and risk factors for depression

Regardless of the age at which a person first experiences symptoms of major depressive disorder, experts believe that the onset of these symptoms may result from a variety of genetic and environmental influences. The following are among the more common factors that may contribute to the development of major depression:

Genetic: Among the evidence that suggests a genetic component to major depressive is the fact that the children and siblings of people who have major depressive disorder are at increased risk for developing the disorder themselves. Also, experts have identified three neurotransmitters, norepinephrine, serotonin, and dopamine, that appear to influence a person’s likelihood for developing major depression.

Environmental: A major negative life change, experiencing a serious illness, the loss of a loved one, and similar experiences are among the environmental factors that may precipitate a major depressive episode. The stress of growing up with parents who struggle with depression and/or substance abuse may also be an environmental influence on the development of major depression. Other environmental influences include being abused or neglected or being exposed to significant stresses and pressures.

Risk Factors:

• Family history of depression or another mental health disorder
• Family history of substance abuse and/or addiction
• Being female (some studies indicate that women are twice as likely as men to develop major depression)
• Personal history of substance abuse and addiction
• Poverty
• Exposure to significant stress
• Trauma
• Dramatic negative life changes

Signs and symptoms of depression

Major depressive disorder does not manifest via identical symptoms in all people. However, the following are among the more common signs and symptoms that may indicate that a person is experiencing major depressive disorder.

Behavioral symptoms:

• Unexplained absences from work
• Failure to perform to one’s potential at work
• Emotional outbursts with no obvious cause
• Engaging in self-harm
• Decreased participation in activities that were once of great importance
• Withdrawal from family and friends

Physical symptoms:

• Fatigue or exhaustion
• Insomnia or hypersomnia
• Increased or decreased appetite
• Headaches and stomachaches
• Generalized muscle and joint pain

Cognitive symptoms:

• Slowed thinking
• Inability to focus or concentrate
• Problems making decisions
• Difficulties with memory
• Memory problems
• Recurrent thoughts of death

Psychosocial symptoms:

• Heightened irritability
• Overwhelming sense of helplessness
• Overwhelming sense of hopelessness
• Extreme feelings of sadness, shame, and/or guilt

Effects of depression

Untreated major depressive disorder can put a person at increased risk for a wide range of negative outcomes, such as the following:

• Developing a co-occurring mental health condition
• Developing a substance use disorder
• Substandard work performance
• Job loss and chronic unemployment
• Financial problems related to substance abuse and/or unemployment
• Social withdrawal and isolation
• Engaging in dangerous, reckless, and other risky behaviors
• Strained or ruined interpersonal relationships
• Family discord, possibly leading to separation and divorce
• Experiencing a sleep disorder
• Suicidal thoughts and attempts

Depression and co-occurring disorders

It is not uncommon for individuals who are struggling with major depressive disorder to also experience a co-occurring mental health disorder such as the following:

• Substance use disorder
• Panic disorder
• Anorexia nervosa
• Bulimia nervosa
• Borderline personality disorder
• Obsessive-compulsive disorder (OCD)