Information on depression


What is depression?

Every person goes through phases in which they feel sad, unhappy or are lacking motivation. In healthy individuals, these are usually temporary periods, lasting only a few hours or a couple of days, and are usually followed by phases characterized by motivation and zest for life. However, in people suffering from depression, the quality of life is impaired over a longer period of time. Negative emotions will persistently overshadow everyday life. Those affected often experience a lack of energy or drive, a loss of interest in activities that once gave them pleasure, or suffer from feelings of guilt or self-doubt. Depression can also be associated with sleep disturbances [1].


What are symptoms of depression?

People suffering from depression experience a “darkening” of their mood and emotional well-being that lasts for weeks or even months. Not all individuals experience depression in the same way. However, most individuals report a deterioration in their quality of life, compared to their previous level of functioning [1, 7].

Some people experience great sadness as the primary symptom of their depression. They feel tearful or hopeless; much in their lives seems pointless. Others will suffer more from a lack of energy or motivation. They feel exhausted, empty, emotionless and like even smallest task takes a giant effort. Still others will experience anxiety, fear or agitation. [14, 7]

These symptoms may also be accompanied by sleep disturbances – including insomnia or excessive sleep. Altered eating behavior can also be an associated symptom, which can lead to weight gain or loss. Many people with depression also report difficulty concentrating or a reduced ability to think. [14, 7]

A extensive list of symptoms can be found below, in the chapter “How is a Depression diagnosed?”.


What are causes and risk factors for depression?

Experts assume that the causes of depression depend on various factors. It is believed that both genetic factors and biological processes, as well as psychosocial factors can all have an influence on the development of depression [1].

Biological processes refer to changes in the brain and the central nervous system. Studies have shown that stimuli are transmitted more slowly in people suffering from depression, and that the metabolism in the brain undergoes changes as well [1, 13].

Genetic factors impact the risk of developing depression. For example, there is an increased risk of experiencing a depressive episode if other family members have already suffered from depression. One study found a total of 102 variants of the genome that were associated with depression. [2]

Special negative events in a person’s life can also play a role; for instance, the death of an important person, a breakup or divorce. Traumatic events such as physical or psychological abuse can also have an impact in the development of depression [1].

We now know that burdensome life circumstances, such as permanent stress or loneliness, as well as certain personality traits (e.g. a pronounced pessimism) can additionally contribute to the manifestation of a depressive episode [1,7].

Other chronic or disabling physical illnesses (e.g., cancer or stroke) may also increase the risk of developing a depressive episode [15]. Substance use disorder can also trigger depression [3]. Other pre-existing mental health conditions, such as an anxiety disorder, may also play a role [1].

Women are 1,5 to 3 times more likely to develop depressive symptoms than men [15]. While the initial onset of depression can occur at any age, one study found that a depressive episode typically first manifests in people between the ages of 20 and 30 [4].


How many people are suffering from depression?

Depression is one of the most common mental illnesses. The lifetime risk of experiencing depression (any form), at least once in one’s life, is estimated at 16-20% [9].

In 2017, depression was the third most common cause of disability worldwide [5]. An article investigating the prevalence of depression among different cultures, noted a lifetime prevalence of 7% in Japan to 21% in France. Most other countries studied, were found to be in a prevalence range between 8-18% [6]. According to a 2013 study, approximately 8.1% of the adult German population aged 18 to 79 stated that they currently suffered from depressive symptoms [9].


How is depression diagnosed?

Generally, an individual suffering from depression will experience a depressed mood or a loss of interest or pleasure. The diagnosis of a depressive disorder requires a reliable and valid examination of the presented symptoms, the respective intensity, as well as an assessment of how long the symptoms have been persisting. Furthermore, possible physical causes must be excluded.

Generally, one can distinguish between main and secondary symptoms. An individual will be diagnosed with depression if they are experiencing at least 5 of the following 9 symptoms, for at least 2 consecutive weeks (Diagnostic and Statistical Manual of Mental Disorders 5th Edition). These symptoms must include at least one of the two main symptoms, which are either:

  • a depressed mood or
  • a loss of interest and pleasure.

In addition, the following symptoms can also occur:

  • a change in weight or appetite,
  • an inability to sleep or excessive sleeping
  • impaired concentration or indecisiveness
  • psychomotor retardation or agitation, meaning slowed or unsettled thoughts and behavior
  • a loss of energy or fatigue,
  • feelings of worthlessness or guilt,
  • thoughts of death, suicidal ideation or suicide attempts.

The symptoms must occur frequently (nearly every day) and must cause distress or impairment to the individual.

A doctor will refrain from diagnosing a depression if the depressive episode can be attributed to substance use or another medical condition [7, 8].


Are there different forms of depression?

Experts and doctors distinguish between different types and degrees of severity of depression.

The following types can be distinguished [1]:

  • Unipolar depressions, like
  • Major Depressive Disorder
  • Persistent depressive disorder (Dysthymia)
  • Seasonal Affective Disorder (SAD)
  • Postpartum depression
  • Bipolar disorder

You can read more about the different forms of depression on the following page.


How is depression related to other illnesses?

Depression is often related to other conditions. This may be related to the fact that depressive symptoms oftentimes are an extreme or even pathological reaction to a difficult situation or excessive psychological stress. In part, the physio-pathological processes of depression are also similar to other mental illnesses. Correct treatment of all co-occurring disorders is essential for successful treatment.

Coexisting or co-occurring disorders are also referred to as comorbidities. One of the most frequent comorbidities in people suffering from depression is anxiety. One study found that up to 85% of people diagnosed with depression, additionally suffer from an anxiety disorder [10]. Other common comorbid disorders include obsessive-compulsive disorder, substance use, alcohol use, post-traumatic stress disorder, or personality disorders. The simultaneous existence of multiple disorders can prolong and complicate treatment [7].

In addition, researchers have found that people are more likely to suffer from depression, if they also have a preexisting chronic condition. These include cardiovascular, metabolic, or neurological disorders [11]. Particularly for people with chronic pain, depressive episodes are not uncommon. Do to the fact that chronic pain creates a constant state of stress for the individual, it can oftentimes trigger depressive symptoms. The coexistence of depression and chronic pain can increase the severity of both conditions [12].


 What are preventive actions?

Depression is a complex, multi-factorial disorder, the development of which is influenced by different factors and circumstances. While a genetic predisposition can mean that some people are more likely to develop depression than others, the factors that can be influenced preventively have more to do with one’ s lifestyle.

On the following page, we have compiled some measures regarding the prevention of depression.


How can depression be treated?

Depression can be treated in a variety of ways.

  • Different types of psychotherapy, such as cognitive behavioral therapy (CBT), or psychodynamic psychotherapy
  • Medication, for example selective serotonin reuptake inhibitors (SSRIs)
  • Other alternative methods, such as light therapy or ketamine-augmented psychotherapy

For a more in-depth overview of therapy options, please see the following page.

Published on 08.02.2022

[1] – ist eine Website des IQWiG. Abgerufen am 05.05.2021. unter

[2] Howard, D. M., Adams, M. J., Clarke, T. K., Hafferty, J. D., Gibson, J., Shirali, M., Coleman, J., Hagenaars, S. P., Ward, J., Wigmore, E. M., Alloza, C., Shen, X., Barbu, M. C., Xu, E. Y., Whalley, H. C., Marioni, R. E., Porteous, D. J., Davies, G., Deary, I. J., Hemani, G., … McIntosh, A. M. (2019). Genome-wide meta-analysis of depression identifies 102 independent variants and highlights the importance of the prefrontal brain regions. Nature neuroscience, 22(3), 343–352.

[3] Khan, A., Faucett, J., Lichtenberg, P., Kirsch, I., & Brown, W. A. (2012). A systematic review of comparative efficacy of treatments and controls for depression. PloS one, 7(7), e41778.

[4] Kessler, R. C., & Bromet, E. J. (2013). The epidemiology of depression across cultures. Annual review of public health, 34, 119-138.

[5] James, S. L., Abate, D., Abate, K. H., Abay, S. M., Abbafati, C., Abbasi, N., … & Briggs, A. M. (2018). Global, regional, and national incidence, prevalence, and years lived with disability for 354 diseases and injuries for 195 countries and territories, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. The Lancet, 392(10159), 1789-1858.

[6] Kessler, R. C., & Bromet, E. J. (2013). The epidemiology of depression across cultures. Annual review of public health, 34, 119-138.

[7] American Psychiatric Pub. APA [American Psychiatric Association] (2018). Diagnostisches und Statistisches Manual Psychischer Störungen DSM-5®  (2. korrigierte Auflage). Göttingen: Hogrefe.

[8] Uher, R., Payne, J. L., Pavlova, B., & Perlis, R. H. (2014). Major depressive disorder in DSM‐5: Implications for clinical practice and research of changes from DSM‐IV. Depression and anxiety, 31(6), 459-471.

[9] Busch MA, Maske UE, Ryl L, et al. Prävalenz von depressiver Symptomatik und diagnostizierter Depression bei Erwachsenen in Deutschland. Ergebnisse der Studie zur Gesundheit Erwachsener in Deutschland (DEGS1). Bundesgesundheitsblatt, Gesundheitsforschung, Gesundheitsschutz 2013;56(5-6):733-9

[10] Tiller, J. W. (2013). Depression and anxiety. The Medical Journal of Australia, 199(6), S28-S31.

[11] Gold, S. M., Köhler-Forsberg, O., Moss-Morris, R., Mehnert, A., Miranda, J. J., Bullinger, M., … & Otte, C. (2020). Comorbid depression in medical diseases. Nature Reviews Disease Primers, 6(1), 1-22.

[12] Sheng, J., Liu, S., Wang, Y., Cui, R., & Zhang, X. (2017). The link between depression and chronic pain: neural mechanisms in the brain. Neural plasticity.

[13] Berger, Mathias (2019) Psychische Erkrankungen Klinik und Therapie (6. Auflage), Elsevier/Urban & Fischer

[14] Mayo Clinic. Depression (major depressive disorder). Abgerufen am 04.02.2022.

[15] DGPPN, BÄK, KBV, AWMF (Hrsg.) für die Leitliniengruppe Unipolare Depression*. S3-Leitlinie/Nationale VersorgungsLeitlinie Unipolare Depression – Kurzfassung, 2. Auflage. Version 1. 2017 [cited: YYYY-MM-DD]. DOI: 10.6101/AZQ/000366.