Depression is an affective disorder

Depressive symptoms are widely spread throughout the population with almost everyone having experienced most of these symptoms at one time or another. Within the class of psychiatric disorders, major depression and dysthymia are two of the main diagnostic categories. They are also often referred to as affective or mood disorders. Dysthymia is generally defined as a mild (although persistent) form of depression. The category of affective disorders also includes other disorders such as bipolar disorder; however this EUphact is limited to major depressive disorder and dysthymia.

Depressed mood and loss of interest are the main symptoms of a depressive episode

The International Classification of Disease (ICD-10) is the most widely recognized system in Europe for describing and defining disorders. The ICD-criteria for a depressive episode are depressed mood, loss of interest and enjoyment, and reduced energy leading to increased fatigability and diminished activity. Marked tiredness after only slight effort is common. Other common symptoms are:

• reduced concentration and attention;
• reduced self-esteem and self-confidence;
• ideas of guilt and unworthiness (even in a mild type of episode);
• bleak and pessimistic views of the future;
• ideas or acts of self-harm or suicide;
• disturbed sleep;
• diminished appetite.

To meet the diagnostic criteria, the symptoms need to be present for at least two weeks. Symptoms typically do not vary from day to day, however there may be a variation in the symptoms during the course of a day. Depression can be described as mild, moderate or severe.

Dysthymia is a mild but persistent form of depression

Dysthymia is generally defined as a mild but persistent form of depression, which lasts at least two years. It mostly starts in young adolescence. The main symptoms of both dysthymia and depression are a persistent depressed mood and a loss of interest or pleasure in daily activities. It is not unusual for people with dysthymia to experience also major depressive episodes. In fact, more than 75% of people with dysthymia will meet the criteria for a major depressive episode at some point in their lives (Keller et al., 1995). Those that suffer from both a major depressive disorder and dysthymia are said to suffer from “double depression” (Klein et al., 2006).

Depression is a recurrent disorder

It is very common for depressive episodes to recur in individuals. Most people (75%-90%) who have experienced an episode of depression will experience at least one more episode in their life (Greden, 2001). There is a general consistency across Europe regarding the course of this illness (Paykel et al., 2005). When symptoms of a depressive episode do not fully subside, the potential for relapse is significantly increased (Judd, 2000). Lower recurrence rates are found in studies of out-patients than in studies of in-patients. Even lower rates of recurrence are found in surveys of the general population (Paykel et al., 2005). This suggests that the likelihood of recurrence is tied to the severity of the symptoms. Dysthymia is also a highly recurrent disorder, with results from a longitudinal study yielding a relapse rate of over 70% (Klein et al., 2006).

Depression often occurs together with other mental disorders

Depression often occurs in connection with other mental disorders. A series of general population surveys in six European countries found that 53.1% of individuals with depression suffered from more than one mental disorder (Alonso et al., 2004). 73.3% of individuals with dysthymia had more than one mental disorder. Depression was most commonly associated with dysthymia and was also linked to anxiety and alcohol disorders in all of the six countries surveyed. It is estimated that 30-40% of all persons suffering from a depressive disorder also suffer from an anxiety disorder and vice versa (Wittchen & Jacobi, 2005).

Depression often occurs together with physical disorders

Depression also often occurs alongside physical disorders. The lifetime prevalence of affective disorders in people suffering from a physical disease is almost double that of people not suffering from a physical disease. Arthritis, cancer, chronic lung disease, cardio-vascular disease and neurological disease are closely related to the prevalence of depression. With increased age, comorbid mental and physical disorders also increase (Wells et al., 1988). The exact nature of the interaction between mental and physical disorders is still under investigation. In some cases physical disease precedes depression (e.g. chronic pain is a risk factor for depression), while in other cases depression precedes physical morbidity. Depression and physical disease can also occur together by chance.