It is now understood that major depressive disorder (MDD) can first occur at any age. Most of the time it appears more noticeably at the start of puberty. The highest rate occurs with people in their 20s, but it is not uncommon for people to experience depression later in life. The course of MDD differs widely. It can last for short periods of time with mild symptoms or long periods of time with severe symptoms, and any variation in between. Typically, clinicians try to figure out how long a person has had symptoms. The longer and more severe the symptoms, the more chances of there being a personality, anxiety, or substance use problem that may be causing or contributing to the depressive symptoms. Recovery is variable as well. If an individual has been depressed for only a few months, they can often recover quickly. However, if a person has severe symptoms, has been depressed for several months to years, or has another condition, such as an anxiety or personality disorder, then recovery may take much longer.
How often one experiences MDD depends on how long they feel depressed and the severity of their symptoms. If someone only feels depressed for a month or so every few years, they probably won't experience MDD very often. The risk for recurring depression is higher in individuals who have had severe, crippling episodes. It is important to note that MDD, particularly with psychotic features, such as hallucinations or delusions, can also transition into schizophrenia.
More women experience MDD than men. However, there are no differences in the age it first occurs, the course, or response to treatment between the genders. The likelihood of suicide goes down the older the person gets, but the course and recovery of MDD does not change with aging.
There are risk factors that can lead people to develop MDD such as temperament, environment, or genetics. Temperament is the combination of mental, physical, and emotional features of a person (their personality). People who have a negative outlook on life or temperament have a natural tendency to develop MDD in response to stressful life events. Stressful events are environmental risk factors that can trigger MDD. These may include the death of a loved one or other major losses such as losing a job or going through a separation or divorce. Other life changes may trigger depression as well. Even normal developmental milestones such as puberty, marriage, or retirement may trigger depression when a particular event is personally distressing to a particular person. For example, a person who loved their job may become depressed after they retire. These stressful situations may be recent, or they may be past events that are strongly remembered for some reason. For example, thinking deeply about stressful past experiences such as emotional, physical, or sexual abuse can trigger an onset of depression. Individuals with Post-Traumatic Stress Disorder (PTSD), who have experienced a traumatic event such as military battle, rape, severe automobile accident or natural disaster are more likely to suffer from depression than people who have not experienced such trauma. When there are multiple and different negative childhood experiences, there is a higher tendency to develop MDD. Major depressive disorder also has runs in families. People who have a parent, brother or sister with major depressive disorder are 2-4 times more likely to develop the disorder themselves than those in the general population. Approximately, 40% of those with MDD have a genetic link to the disorder.
There are also disorders or medical conditions that can increase the risk for developing MDD or making it worse. Examples include substance use, anxiety disorders, and borderline personality disorder. In these situations, treatment and recovery depends on finding the true cause of MDD. Long-term or crippling medical conditions such as diabetes, morbid obesity and heart disease are also risk factors for MDD. There is currently no lab test (such as a blood test or brain scan) that can confirm whether a person has MDD. However, some lab tests can appear different than normal during an active depressive episode. For example, differences in measurements of electrical activity in the brain during sleep have been found in 90% of people who are hospitalized for MDD. Even people with depression who do not have symptoms severe enough to require hospitalization often show these differences. Other differences in brain chemicals and hormones also occur with depression. At this time, none of these tests are reliable or specific enough to prove that the cause is major depressive disorder.
Even though lab tests aren't used to diagnose depression, doctors will often request them. These can be helpful in finding other conditions such as thyroid trouble, cancer, arthritis, and other diseases that might be causing the depressive symptoms. Later in this center, we will discuss more about how clinicians diagnose depression using lab tests, psychiatric interviews and self-report questionnaires. Symptoms of Major Depressive Disorder usually develop over a few days or weeks. Many people feel anxious or mildly depressed for a while before a full depressive episode becomes apparent. Often, the symptoms eventually disappear and functioning returns to normal. The DSM-5 provides labels that describe the course of a person's Major Depression:
- "full remission" means there are no current depressive symptoms
- "partial remission" means that the person currently has fewer than five depressive symptoms or has had no symptoms at all for less than two months;
- "chronic" means that a person has met all of the diagnostic criteria for Major Depressive Disorder for two or more years.
Approximately 20-30% of people with Major Depressive Disorder experience partial remission of symptoms, while 5-10% of people have chronic MDD.
Suicide is a risk during times of MDD episodes. Women have a higher risk of suicide attempts, but their risk for being successful is lower. This is because they often choose methods such as an overdose rather than use of a gun. A history of suicide attempts or threats greatly increases the risk of a successful suicide attempt, but it is important to note that most completed suicides are done by those who have never attempted it before.