Too much depression?

There's been a fair bit of media coverage of Gordon Parker's contention that depression is overdiagnosed (e.g. Nick Johnstone in the Guardian). Parker argues that drug company influences are promoting this over diagnosis of mild and subthreshold depression, which seems strange given that NICE recommends antidepressants not be used for mild depression:

"Antidepressants are not recommended for the initial treatment of mild depression, because the risk–benefit ratio is poor."

Which isn't to say that the government hasn't willfully and unaccountably failed to provide resources for cognitive behavioural therapy (6 month waiting lists are almost useless) which has proven cost-effectiveness when compared to antidepressants.

He basis his claims on a prospective study of teachers where he found that:

"By 1993, 79% of teachers in our cohort (in their late 30s) had already met symptom and duration criteria for lifetime major, minor, or subsyndromal depression (unpublished data)."

Subthreshold depressions (including subclinical/minor, recurrent brief, and subsyndromal depressions) are defined in similar ways to major depressive episodes but with generally less symptoms or <2 weeks duration - these are often more usefully considered research, rather than clinical definitions, and were created to capture the experience of people with significant impairment in their lives yet who didn't meet the criteria for major depression. The requirement for impairment in social functioning in these definitions - you aren't depressed if it doesn't have a detrimental effect on how you carry out normal functions is fundamental.

I'll repeat again what Parker said about those teachers, they "met symptom and duration criteria for lifetime major, minor, or subsyndromal depression" - since he doesn't specify that they met criteria for impaired function, or that they didn't meet exclusion criteria for reactive depression, I must assume that what he's saying is that they experienced two or more symptoms for two weeks, without necessarily any adverse effects on their lives - that is somewhat different to claiming that they all met criteria for major depression! It is a bit like the claim that some 10% of people have, at some point in their lives, heard voices - and therefore people with schizophrenia aren't ill despite the massive deleterious effects on their lives.

Johnstone makes some odd points about real depression being due to lack of serotonin and thus treating people without it with SSRIs is bad - presumably he is unaware of how little evidence there is that depression has anything to do with serotonin other than that we know antidepressants increase serotonin levels (as does ecstasy). JP's rather uncharitable reading is that he's trying to draw a distinction between his real depression and those saps that just think they're depressed. He also talks about antidepressant medication prescriptions as if they accurately reflect the number of people with depression - unlikely given the widespread use of SSRIs for anxiety and tricyclics for neuropathic pain:

"Last year, in Britain alone, 31m prescriptions were handed out for antidepressants, a 6% rise on 2004, suggesting that we're either collectively bending under the strain of modern life or doctors are far too freely handing out prescriptions.
...
the danger with overdiagnosing a bad patch in life as clinical depression is that doctors are using medication to treat brains that fundamentally work the way they are supposed to."

Criteria for major depression in DSM-IV-TR are:

A. Five (or more) 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) depressed mood or
(2) loss of interest or pleasure.
Note: Do not include symptoms that are clearly due to a general medical condition, or mood-incongruent delusions or hallucinations.

(1) depressed mood most of the day, nearly every day, as indicated by either subjective report (e.g., feels sad or empty) or observation made by others (e.g., appears tearful). Note: In children and adolescents, can be irritable mood.
(2) markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day (as indicated by either subjective account or observation made by others)
(3) significant weight loss when not dieting or weight gain (e.g., a change of more than 5% of body weight in a month), or decrease or increase in appetite nearly every day. Note: In children, consider failure to make expected weight gains.
(4) Insomnia or Hypersomnia nearly every day
(5) psychomotor agitation or retardation nearly every day (observable by others, not merely subjective feelings of restlessness or being slowed down)
(6) fatigue or loss of energy nearly every day
(7) feelings of worthlessness or excessive or inappropriate guilt (which may be delusional) nearly every day (not merely self-reproach or guilt about being sick)
(8) diminished ability to think or concentrate, or indecisiveness, nearly every day (either by subjective account or as observed by others)
(9) recurrent thoughts of death (not just fear of dying), 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 (see p. 335).

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 (e.g., a drug of abuse, a medication) or a general medical condition (e.g., hypothyroidism).

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.

note that the DSM distinguishes between Major Depressive Disorder that has been characterised by only a single episode, versus recurrent major depressive episodes. Dysthymia is defined as

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. Note: In children and adolescents, mood can be irritable and duration must be at least 1 year.

B. Presence, while depressed, of two (or more) 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 decisions
(6) feelings of hopelessness

C. During the 2-year period (1 year for children or adolescents) of the disturbance, the person has never been without the symptoms in 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 (1 year for children and adolescents); i.e., the disturbance is not better accounted for by chronic Major Depressive Disorder, or Major Depressive Disorder, In Partial Remission.
Note: There may have been a previous Major Depressive Episode provided there was a full remission (no significant signs or symptoms for 2 months) before development of the Dysthymic Disorder. In addition, after the initial 2 years (1 year in children or adolescents) of Dysthymic Disorder, there may be superimposed episodes of Major Depressive Disorder, in which case both diagnoses may be given when the criteria are met for a Major Depressive Episode.

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 (e.g., a drug of abuse, a medication) or a general medical condition (e.g., hypothyroidism).

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