Diagnosis of depressive disorders

Research programmes, such as this thesis, usually apply the DSM classification rather than the International Classificaton of Disease (ICD) (WHO) as it provides more detailed guidelines for case definition. According to DSM-IV (APA, 1994) depressive disorders take one of three forms: major depressive episode (MDE), dysthymic disorder or "depression not otherwise specified", which includes several forms of briefer or milder periods of depression. Major depressive disorder (MDD) consists of one or more MDE (Figure 1.).

MDE may be classified as mild, moderate or severe (with or without psychotic features), based on the number and severity of symptoms, and the degree of functional disability and distress (APA, 1994, 2000). DSM-IV and ICD-10 diagnoses of MDD differ slightly: in ICD-10 the core symptoms are added with loss of energy and two of the three core symptoms have to be present. Also worthlessness and inappropriate guilt are defined as separate symptoms.

Dysthymic disorder in DSM-IV consists of chronic but milder symptoms than MDE (Figure 2.).

Figure 1. The diagnostic criteria for Major Depressive Episode in DSM-IV (APA, 1994).

A. Five of the following symptoms have been present during the same 2-week period and represent a change from previous functioning: at least one of the symptoms is either 1) or 2)

1) Depressed mood most of the day, nearly every day, as indicated by either subjective report or observation made by others

2) Markedly diminished interest or pleasure in all, or almost all activities most of the day, nearly every day

3) Significant weight loss when not dieting or weight gain, or decrease or increase in appetite nearly every day

4) Insomnia or hypersomnia nearly every day

5) Psychomotor agitation or retardation nearly every day 6) Fatigue or loss of energy nearly every day

7) Feelings of worthlessness or excessive or inappropriate guilt nearly every day

8) Diminished ability to think or concentrate or indecisiveness nearly every day

9) Recurrent thoughts of death, recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide

B. The symptoms do not meet criteria for a Mixed episode

C. The symptoms cause clinically significant distress or impairment in social, occupational or other important areas of functioning

D. The symptoms are not due to the direct physiological effects of a substance or a general medical condition

E. The symptoms are not better accounted for by bereavement, i.e., after the loss of a loved one, the symptoms persist for longer than 2 months or are characterized by marked functional impairment, morbid preoccupation with worthlessness, suicidal ideation, psychotic symptoms or psychomotor retardation.

Figure 2. The diagnostic criteria for Dysthymic Disorder in DSM-IV (APA, 1994).

A. Depressed mood for most of the day, for more days than not, as indicated either by subjective account or observation by others, for at least 2 years

B. Presence, while depressed, of two of the following:

1) Poor appetite or overeating 2) Insomnia or hypersomnia 3) Low energy or fatigue 4) Low self-esteem

5) Poor concentration or difficulty making decision 6) Feelings of hopelessness

C. During the 2-year period of the disturbance, the person has never been without the symptoms of Criteria A and B for more than 2 months at a time

D. No Major Depressive Episode has been present during the first 2 years of the disturbance; i.e., the disturbance is not better accounted for by chronic Major Depressive Disorder, or Major Depressive Disorder, in partial remission

E. There has never been a Manic Episode, a Mixed Episode or a Hypomanic Episode, and criteria have never been met for Cyclothymic Disorder

F. The disturbance does not occur exclusively during the course of a chronic Psychotic Disorder, such as Schizophrenia or Delusional Disorder

G. The symptoms are not due to the direct physiological effects of a substance or a general medical condition

H. The symptoms cause clinically significant distress or impairment in social, occupational or other important areas of functioning

Moreover, a substantial proportion of subjects with disabling depressive symptoms fail to meet the diagnostic criteria for MDD or dysthymia, as demonstrated in many studies on primary care patients, such as the World Health Organization (WHO) study on Psychological Problems in General Health Care (PPGHC) (Sartorius et al., 1996). Some of these subsyndromal conditions are included in the category Depressive disorder not otherwise specified (APA, 1994). In literature the use of the terms describing subsyndromal depressions is unfortunately diverse, including syndromes with varying numbers of symptoms, with varying duration and causing varying degrees of impairment (Pincus et al., 1999).

Subsyndromal depressive symptoms, although not a diagnostic entity, is a clinical condition proposed by Judd in order to further analyse the pleomorphism of the depressive spectrum in the National Institute of Mental Health (NIMH) Epidemiological Catchment Area (ECA) Program (Judd et al., 1997). It was there defined as "at least two current depressive symptoms, present every day for most of the time, at least two weeks, in persons not meeting criteria for MDD, minor depression or dysthymic disorder". Thus it could refer to residual symptoms of a past MDE or a prodromal of a future MDE (Judd et al., 1997). In this thesis the definition suggested by Judd (1997) is used for subsyndromal depressive disorder with one exception of demanding one of the current symptoms to be a core symptom of MDE.

For minor depression (MinD), although not considered an official clinical diagnosis, the American Psychiatric Association defined research diagnostic criteria in Appendix B of the DSM-IV (APA, 1994). The essential features are identical to MDE in duration, but involve fewer symptoms and less impairment. An episode involves either sad or depressed mood or loss of interest or pleasure in nearly all activities. In total, at least two but less than five additional symptoms must be present.

The Appendix B in DSM-IV (APA, 1994) also defines diagnostic criteria for recurrent brief depressive disorder, where the episodes are identical to MDE in the number and severity of symptoms but do not meet the 2-week duration requirement. The episodes last at least 2 days but less than two weeks. Episodes must recur minimum once a month for a period of 12 consecutive months (APA, 1994).

4.3.1 Subgroups of depressive disorders

Diagnostic specifiers in DSM-IV define descriptively important distinctive features of depressive episode for the purposes of research or treatment choice (APA, 1994). Psychotic features may be present in a severe MDE, and includes presence of either hallucinations or delusions. Psychotic depression, even more than melancholic depression, appears to be relatively stable over repeated episodes (Coryell et al., 1994). Melancholic features of DSM-IV MDE include lack of reactivity to pleasurable stimuli, diurnal variation of symptoms, inappropriate guilt, early morning awakening, marked psychomotor change, either retardation or agitation, and significant loss of appetite or weight loss. According to Parker (Parker et al., 2005) melancholic features and psychotic features may represent a distinctive form of severe depression arising from different pathophysiology than other forms of depression. Depression with atypical features was first recognized in a subset of patients with depression who preferentially responded to the monoamine oxidase inhibitors in contrast to patients with melancholic depression (Stewart et al., 2007). Atypical features include mood reactivity and two or more of the following: increased appetite or weight gain, hypersomnia, leaden paralysis and long-standing interpersonal rejection sensitivity in non-psychotic, non-melancholic MDE or dysthymic disorder (APA, 1994). The current definition of atypical features appears problematic as interpersonal rejection sensitivity and leaden paralysis may have their phenomenological base in anxiety rather than depression (Parker et al., 2002). Seasonal pattern depressions have an apparent regular onset and disappearance during certain times of the year. In the Northern hemisphere the most common pattern is autumn or winter depressions (APA, 1994).

Postpartum onset specifier can be applied to a MDE if the onset is within 4 weeks after the delivery of a child (APA, 1994).

4.3.2 Multiaxial assessment

Multiaxial system of DSM-IV (APA, 1994) involves an assessment on several axes, each of which refers to a different domain of information that may help the clinician plan treatment and predict outcome. In this thesis Axis I (clinical disorder), Axis II (personality disorder) and Axis III (general medical condition) are used.