Clinical depression's not common, to my mind.
Unhappiness is very common. Unhappiness is an emotion, not an illness.
A little bit of unhappiness, or a lot of it, is a varying intensity of one normal human emotion, so even intense unhappiness is but part of life's rich tapestry and unwelcome though it may be, it's not an illness or a disorder.
Although I'm not a slave to diagnostic checklists, they certainly have a place and shape my thinking. On discussing someone's experiences the details, the nuance, the context, they matter. On considering someone's mental state, eliciting psychopathology and ascribing significance to it/formulating it in other ways and discounting it matters. History taking and mental state examination are clinical activites, not check lists and tick boxes, so there's always room for inclusion of folk and diagnosis of depression for people who don't present with a perfect list for the diagnosis to be textbook.
With this caveat that diagnosis is clinical, contextual and will at times vary from diagnostic lists, I'd concede that most of the time diagnosis falls within accepted frameworks. My training and practice is using the World Health Organisation's International Classification of Diseases, 10th Revision (ICD-10).
It's very useful. It's not just determining what a diagnosis is, it also determines what a diagnosis isn't. For example, "alcoholic" and "alcoholism" aren't in there so aren't and can never be formal diagnostic labels I make. Using the ICD-10 framework engenders a more transparent, consistent, reasoned process to formulation and diagnosis which I find helpful.
Low mood is very very common. Endogenous functional clinical depression arising through abnormal serotin/neurochemistry balance, much less so.
Does this distinction matter?
People with clinical depression have abnormal brain chemistry, this causes illness which has physical and psychological symptoms and signs. By inference, the chemical pathology causing this upset can benefit from chemical solutions (antidepressants). Clinical practice illustrates this, clinically depressed patients do get better on antidepressants.
People may also have low mood because their situation's ghastly and gets them down. If you're down because you're lonely or hungry or in severe chronic pain or you're dying or your loved one's dying or you're abused then is your intense unhappiness clinical depression, caused by chemical illness, so will happiness come in a tablet? Unfortunately not.
People may have low mood through organic syndromes. Stroke damage within the base of the brain or poor blood supply causing ischaemic damage within the diencephalon damages the limbic system, the mood centre in the brain. I've patients who have had cheery dispositions, had stroke damage, are depressed and it's through structural organic brain damage caused by the stroke. Antidepressants have little place.
If unhappiness is sometimes situational and sometimes through structural brain changes, then how do we pick up those unhappy folk who have clinical depression? This matters since such folk with severe clinical depression usually profit from antidepressant drug therapy.
What are the ICD-10 diagnostic criteria?
You need to be depressed for 2 weeks. Being depressed for a few days, then being okay, isn't enough.
You need to be depressed in most situations, most of the time. If you're low for the whole day, but you're okay when your kids visit and take you out to the pub for Sunday lunch, that's not clinical depression. Neurochemistry doesn't rapidly shift as you change from one room to another, so shifting from alone in your house to company in a pub suggests a more reactive/situational cause for unhappiness, or loneliness, rather than being consistent with the chemical illness of clinical depression.
Okay, you've someone with low mood, they've had low mood for 2 weeks, their mood's persistent and pervasive, isn't that just them being unhappy? Yes, it is. To be clinical depression you need to have a number of features :
· Depressed mood that is definitely abnormal for the person, present most of the day, almost every day, largely uninfluenced by circumstances, sustained for at least 2 weeks
· Loss of interest or pleasure in activities
· Decreased energy or increased fatiguability
· Loss of confidence or self esteem
· Unreasonable feelings of self-reproach or excessive and inappropriate guilt
· Recurrent thoughts of death or suicide, or suicidal behaviour
· Diminished ability to think or concentrate
· Changes in psychomotor activity (with agitation or retardation)
· Sleep disturbance
· Change in appetite (decrease or increase) with corresponding weight change
How many of the features correlates with severity :
Mild depressive episode :
"Two or three symptoms are usually present. The patient is usually distressed by these but will probably be able to continue most activities."
Moderate depressive episode :
"Four or more symptoms are usually present. The patient is likely to have great difficulty in continuing with ordinary activities."
Severe depressive episode :
"Eight or more symptoms must be present. Symptoms are marked and distressing, suicidal thoughts and acts are common and a number of ‘somatic’ symptoms are usually present."
The additional somatic symptoms that usually are present would consist of :
· Loss of interest or pleasure in activities
· Reduced emotional response
· Waking in the morning 2 or more hours before the usual time
· Depressed mood is worse in the morning
· Objective evidence of psychomotor retardation or agitation (reported/remarked on by another person)
· Marked loss of appetite
· Weight loss (5% or more of body weight in the last month)
Marked loss of libido
This is important, I believe, because if we diagnose clinical depression when it isn't then people get the wrong treatment. We know from last year's JAMA paper that antidepressants work no better than placebo in mild, moderate or severe depression and only are shown to work better than placebo in very severe depression. We know from a paper in this month's British Journal of Psychiatry that, still, antidepressants don't work in mild depression. Okay okay, studies show us averages and trends, individual patients may respond brilliantly to antidepressants despite have mild or moderate depression, but on average response is the same with antidepressant or placebo.
If we need 2, 4 or 8 core features of depression, and typically there're also some of the 7 somatic features of depression, to my mind that's getting to a much more specific (and smaller) group than all people who have intense low mood.
It's also a harder way to work. If we equate intense low mood with depression, so refer for psychological therapy and start an antidepressant, then everything's done and is easy. If we're sleuthing out who has a depression that's reactive/situational, who has a depression that's organic/structural and who has a depression that's endogenous/chemical, that's a more involved assessment. Worse, if only the last group generally profit from an antidepressant, we're then having to help people with ghastly low mood, suicidality and feelings of not coping through support that doesn't typically include antidepressants. We have to do more than just offer a prescription and refer to a psytchologist.
Harder work, both in assessment and interventions, but to my mind increasingly it's looking untenable to work in any other way.