Depression is a state of persistent low mood that affects most aspects of daily life.1 People experiencing depression often feel disinterested in the things that usually make them happy, a symptom called anhedonia. During depressive moods, a person may feel a sense of worthlessness, guilt, and hopelessness that isn’t necessarily justified by their current life circumstances.
Alongside mood disturbances, other symptoms of depression are sometimes less obvious, such as fatigue, reduced or increased appetite, changes in sleep, and brain fog. Depressive moods are symptoms of some of the most common mental disorders affecting people at all life stages.
There are many effective treatments for depression, but whether they work or make things worse is tied to the disorder causing their depression. It’s therefore critical to identify the cause of one’s depression. While only a licensed medical professional can make the call on what kind of depression you are experiencing, understanding the different kinds of depression can help you and your care team make a more accurate diagnosis.
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Major depressive disorder (MDD) is the most common form of depression and the third-most common disease worldwide.2 Around 12 percent of people will experience MDD at some point in their life, with women experiencing it twice as often as men. MDD is most prevalent in middle age but can occur at any phase of a person’s life.
Regardless of when it occurs, MDD is a serious issue that can impact daily life and significantly increase the risk of self-harm and suicide. This condition is thought to be caused by imbalances in certain brain chemicals, although more recent research has shown it to be much more complex.
Diagnosing Major Depressive Disorder
The process of diagnosing MDD is a process of ruling out alternatives. To be diagnosed with MDD, a person must experience five of the key depressive symptoms for most of the day over a period of at least two weeks. Physiological causes, life events, and other mental disorders must be excluded, which is essential for management.
Treatment usually involves psychotherapy and antidepressant medications called selective serotonin reuptake inhibitors (SSRIs).
Disruptive Mood Dysregulation Disorder
Disruptive mood dysregulation disorder (DMDD) is a newly classified mental disorder that affects children.3 It is characterized by persistent severe irritability and outbursts and is usually accompanied by periods of sustained low mood.
To be considered for DMDD, a child must display this state of agitation for one year by the time they are 10 years old, with breaks from symptoms lasting three months at most. Importantly, patients must not have experienced manic episodes typical of bipolar disorder. In addition, they must be ruled out for oppositional defiant disorder, which is characterized by only one outburst per week instead of three.
Persistent Depressive Disorder (Dysthymia)
Persistent depressive disorder, also called dysthymia, is a form of long-term depressive mood that does not meet the threshold for MDD.4 Dysthymia episodes generally last for at least two months and occur off and on over several years. The time between these episodes must be two months or shorter.
While the symptoms of dysthymia are generally not as severe in the moment, the persistent nature of the disorder can cause long-term impairments to quality of life that are worse than MDD in some cases. Despite these differences, it is usually treated identically to MDD.
Postpartum depression is a sustained form of depression that occurs in the first six weeks after childbirth.5,6 Lasting much longer and being more severe than the typical “baby blues,” postpartum depression causes significant distress and can affect early bonding with a person’s child. Unfortunately, because of the social stigma, many people experiencing postpartum depression keep it to themselves and don’t get the support they need.
Postpartum depression is thought to be caused by changes in reproductive hormones that generally occur after childbirth, with genetic, psychological, and social factors influencing one’s likelihood of developing it. Treatment is similar to MDD, but care must be taken when selecting medications if the individual experiencing postpartum depression is breastfeeding.
Seasonal Affective Disorder (SAD)
Seasonal affective disorder (SAD) is a kind of depression linked to seasonal changes in sunlight.7-9 Accordingly, it is more common in higher latitudes when the days are shorter during winter. It is caused, in part, by low levels of vitamin D, which is activated by exposure to sunlight. Because of this, it has historically been treated with light therapy, where a person is exposed to a light source mimicking the natural spectrum of sunlight.
Premenstrual Dysphoric Disorder (PMDD)
Premenstrual dysphoric disorder (PMDD) is a form of depression that occurs regularly throughout a person’s menstrual cycle, peaking during menstruation.10,11 While some degree of low mood often occurs during this period, up to 8 percent of people who menstruate have significant depressive symptoms that get in the way of their daily life. In addition to depressive symptoms, a person experiencing DMDD may also feel increased anxiety levels.
PMDD is thought to be caused by sex hormones, which may explain why transgender people with ovaries who take testosterone therapy experience a reduction in their symptoms. DMDD can be treated with exercise, antidepressants, and hormonal birth control.
Bipolar disorder is a mood disorder that is characterized by regular, periodic extreme shifts in mood.12,13 There are three mood states most common in bipolar disorder: depression, mania, and hypomania. Bipolar depression is similar to other depressive states, while mania is an excessively elevated mood where a person feels on top of the world and acts impulsively to the degree that it causes problems in their life. Hypomania is a subthreshold form of mania that, while disruptive and distressing for others, does not significantly impact a person’s daily activities.
There are two main forms of bipolar disorder: type I and type II. People with type I bipolar disorder experience manic phases, while people with type II do not, primarily having depressive episodes. Diagnosing bipolar disorder is important, as some antidepressants for MDD can trigger or exacerbate a manic episode.
Depressive psychosis is a form of depression that occurs alongside symptoms of psychosis, which include delusional beliefs and hallucinations.14,15 Depressive psychosis most commonly occurs in people with other disorders of psychosis, like depression and severe bipolar type I. Patients with depressive psychosis are at a higher risk of self-harm and inpatient care. Management is usually more intensive and based on the other underlying conditions a person experiences.
Situational depression, often falling under the category of adjustment disorder, is a state of depression that is caused by significant life changes.16-18 It is one of the most commonly diagnosed mental disorders and affects up to 9 percent of people.
To be considered situational depression, a person must be able to identify a key life event that has triggered it, such as changes in employment or relationship difficulties. Bereavement is generally excluded from the diagnostic criteria, as it is depression that is preexisting from another condition.
Situational depression generally resolves after six months and is usually treated with psychotherapy.
Atypical depression is a disorder that shares many features with MDD but has some key differences.19,20 In atypical depression, a person may not meet all the criteria for MDD but will have unique symptoms, like heightened sensitivity to interpersonal rejection and leaden paralysis, a feeling of heavy weight in the limbs.
Unlike MDD, atypical depression may respond better to a class of drugs called monoamine oxidase inhibitors (MAOIs).
Treatment-resistant depression (TRD), as the name implies, is a form of depression that fails to respond to at least two different kinds of antidepressant treatments21. As a result, TRD is more difficult to manage and has a lower rate of recovery than other forms of depression.
In recent years, new forms of treatment have shown great promise in treating TRD, including psychedelics, ketamine, and transcranial magnetic stimulation, which involves the application of targeted magnetic fields to the brain without surgery.
Some medications and drugs of abuse can cause depressive symptoms, called substance-induced depression.22 While withdrawing the causative substance is a key part of treatment, underlying conditions and life circumstances usually drive substance use disorders. As a result, treatment must focus on the cause of the substance use. Substance-induced depression is common in people with alcohol or opioid use disorders.
There are many different disorders that cause depression, each with its own unique treatment strategies. Getting an accurate diagnosis is the first step to recovery and symptom relief. While the process of finding an effective therapy for your condition can be arduous, the right treatment can make a huge difference in your quality of life and overall well-being.