Depression is a serious and complex condition, that can have a large impact on social interactions, work, and the ability to function in daily life. Symptoms can vary greatly, depending on the severity and the type of the depression. The current state of research has shown that the right kind of therapy can help alleviate depressive Symptoms, such as helplessness, feelings of worthlessness, distractibility, as well as agitation and restlessness. However, the first step to getting the right treatment, is the right diagnosis. Therefore, it is fundamental for those affected, as well as their friends and family, to know and recognize the most important forms of depression.

In general, one can distinguish between unipolar and bipolar depression. The following paragraphs give an overview of several important forms of unipolar depression as well as bipolar depression.

Unipolar depressions are the most common type of depression [1]. They are classified as affective or mood disorders and are associated with the “typical symptoms” of depression, such as feelings of sadness, emptiness or hopelessness, or loss of interest and drive [1]. Many patients additionally suffer from concomitant physical conditions  [2]. However, in order to be considered  pathological, these symptoms must be present for a prolonged period of time [9].

Research has shown that within one year, about 7.7% of the German population is affected by unipolar depression. Thus, about 6.2 million people in Germany suffer from this type of depression within a period of 12 months [1].

Commonly, when people talk about “depression,” they are usually referring to the main form of the unipolar type: the major depressive disorder. Depending on the number of symptoms and the intensity, a distinction is made between mild, moderate and severe depressive episodes, that can last from weeks to months. The natural course and outcome of a major depressive disorder can vary greatly between individuals: While some people experience only one episode in the course of their lives, others may develop several depressive episodes [9]. On average, untreated depressive episodes begin to subside after 3-4 months. The probability of developing a subsequent episode increases with each additional episode experienced. However, this is only true, if the depression is left untreated [10].

Dysthymia translates as “discontent” or “displeased disposition” [5]. In the ICD-10 (an international classification system by the WHO) it is classified as an affective or mood disorder and belongs to the unipolar depressions [11]. According to the 2013 German Health Interview and Examination Survey for Adults (DEGS1), approximately 2% of the German population (self-reportedly) suffers from dysthymia [3].

The reported symptoms closely resemble those of a major depressive disorder. The main difference lies in the intensity and duration of the symptoms: While in dysthymia the symptomatology tend to be less severe than in major depression (e.g. only mild sadness), they are often latently present for many years (at least 2 years). Although affected individuals often suffer severely due to the persistent symptoms and experience subjective impairments in their everyday lives, most individuals are still able to handle their everyday tasks [1]. In many cases, people suffering from dysthemia will, after a period of time, no longer even notice this dampening of their spirit or gradually resign themselves to its existence. Often this form of depression is only recognized when, for instance, due to a crisis, a patient develops a full syndrome of major depression, in addition to their dysthymic disorder. Experts appropriately refer to this as “double depression” [1].

Symptoms of dysthymia often first appear in childhood, adolescence, or young adulthood and usually have a persistent and chronic trajectory. Those affected have an increased risk of developing major depression in the course of their lives [10]. Therefore, it is extremely important to recognize, react and treat the symptoms of dysthymia quickly and appropriately.

The DSM-5 (a classification system for mental disorders), classifies SAD as a type of recurrent unipolar depression: Major Depressive Disorder with Seasonal Pattern [9]. The best-known form of SAD is also known as “winter depression”. In this case, a depressive episode repeatedly occurs at a specific time of year (typically in autumn and winter), with characteristic symptoms (e.g. depressed mood, listlessness, etc.) [4]. Research suggests that a light deficiency contributes to the development of SAD, and that the symptoms are very likely in part related to a lack of serotonin in the brain [7]. Light therapy is nowadays considered the treatment of choice for seasonal depression [1].

The DSM-5 categorizes depression with peripartum onset (shortly before, during, or shortly after childbirth) as a specific subcategory of major depression. Symptomatically, depression with peripartum onset is similar to depressive disorders that occur independently of pregnancy and childbirth [9]. It is believed that both neuro-chemical and hormonal, as well as psycho-social factors are involved in the development [16].

In general, 10-15% of women are diagnosed with postpartum depression (PPD) [13], and approximately 50% of PPD already begin during pregnancy [1]. Postpartum depression should not be confused with the “baby blues”: mood swings that occur in approximately 50-80% of all delivering women in the first few days after delivery, but subside after a few hours to days. However, some women may experience a gradual transition from “baby blues” to PPD [8]. Often, postpartum depressions are detected too late or not at all, as many women conceal their symptoms as a result of social norms and feelings of shame. The correct diagnosis and treatment is vital, as the symptoms of PPD can strongly influence the ability of mothers and their babies to bond, resulting in lasting effects on their relationship and the child’s development [14]. In some cases, untreated peripartum depression can lead to chronic depressive symptoms and, in some extreme instances, is associated with suicide [15].

Even though the image of mental illness is gradually changing in society, peripartum depression is often still a topic that is taboo. For example, relatives frequently mistakenly think that they are making things worse by voicing their concerns, when the opposite is true: Whether you yourself are affected or a family member or friend: Talk about it! Remember that many women are affected by peripartum depression – you are not alone! Seek advice and help. Nowadays, there are many ways to successfully treat depression.

Bipolar depression is also a form of affective disorder. It occurs episodically, i.e. alternating between phases of no symptoms and phases with clear signs of illness. However, in contrast to unipolar depression, bipolar depression (formerly known as “manic-depression”) is characterized by a fluctuation of one’s mood between two opposing poles. These emotional fluctuations go far beyond the usual level.

Affected individuals experience extreme highs during which they exhibit abnormally elevated or irritable mood, as well as a persistent increase in activity and performance for at least a week. Oftentimes, they will experience a decreased need for sleep, racing thoughts, are highly distractible and will exhibit risky and reckless behavior (e.g. acquiring large amounts of debt). A severe manic episode can even lead to delusional states (mostly delusions of grandeur) and hallucinations [11]. These phases of extreme elation and activity alternate with extreme low phases that are symptomatically equivalent to an episode of major depression. Individuals suffering from bipolar disorder often describe their emotional state as going from the top of the world to down in the dumps. However, there are also mixed affective episodes in which manic and depressive symptoms do not alternate but occur simultaneously [12].

The mechanism underlying bipolar disorder are still not 100% clear. Similar to unipolar depression, it is assumed that both genetic and biological, as well as environmental influences and personality traits play a decisive role [6].

The probability of developing bipolar depression in one’s lifetime is about 3% and often manifests itself in adolescence and young adulthood. Unfortunately, on average, it takes 5 to 10 years after the first onset of symptoms for patients to be properly diagnosed and adequately treated [6].

Due to the severity of the symptoms, many affected individuals experience a serious impairment of their day to day level of functioning. However, if correctly diagnosed and with individual and appropriate therapy, most people suffering from bipolar disorder can regain their quality of life.