Monday, April 20, 2015

Childhood Adversity and Major Depression

A very consistent result in the epidemiological literature is the association between childhood adversity and the subsequent occurrence of major depression during adulthood. More recently, this concept has been expanded with studies reporting associations between childhood adversity and a large number of different adult health outcomes (e.g. cardiovascular disease). A weakness in this literature is that most of the studies arise from retrospective assessment of childhood adversities - which is problematic since peoples' perceptions of their childhoods could easily be influenced by their adult health status. We recently sought to get around this problem by linking a childhood survey to data collected later, during adulthood. There were two outcomes that stood out as being strongly related to childhood adversity: depression and smoking. These are, of course, related outcomes since smoking is strongly related to depression in adolescents, who may smoke to self-medicate and depressed adolescents may also be at much higher risk of becoming nicotine dependent. These findings, summarized here, suggest that depression may be the "lynch pin" linking childhood adversities to later health problems through intermediate mechanisms such as smoking. This may provide an opportunity (management of depression) to prevent many of the later-life health problems that seem to be associated with adverse childhood events.

Thursday, April 16, 2015

Prevalence of Bipolar I and II Disorder in Canada

There have only been two national surveys of mental health in Canada. One of these was conducted in 2002 (the CCHS 1.2) and a second one in 2012 (CCHS-MH). The first survey provided an estimate of bipolar disorder prevalence, see here. This prevalence was higher than expected, so a modified instrument that distinguished the two main types of Bipolar Disorder (I and II) in the 2012 survey. The prevalence has been revisited by Keltie McDonald, an MSc student in epidemiology at the University of Calgary. She found what seemed to be a more plausible prevalence, about 0.9% (traditionally, it has been believed that about 1% of the general population have Bipolar Disorder). However, there some very substantial inconsistencies also observed, e.g. few people with bipolar disorders were taking lithium, and few who reported that they had been diagnosed with Bipolar Disorder were detected by the version of the interview used in the survey. This paper raises some questions about the accuracy of research diagnostic interviews to accurately assess this condition. The result is not actually very surprising. The epidemiological diagnostic interviews used in this type of survey follow inflexible scripts and are well known not to perform well for all diagnoses. It is likely that the best way to study this condition will need to use data from other sources, such as anonymous, aggregate statistics from the health system, e.g. see another paper by Bulloch et al.  

Thursday, April 9, 2015

Stigma against depression in Canada

A recent paper by Dr. Heather Stuart, of Queens University has addressed the question of whether there is stigma against depression among the general public in Canada. She used data from a large national "Rapid Response" survey conducted by Statistics Canada. The survey focussed on people who had sought treatment for mental health - Sadly, a large proportion reported that they believed that others stigmatized depression (about half), whereas one third reported that they themselves had encountered stigma. The full test of the paper is available here.

Models and Metaphors for Major Depression

Since major depression is a condition that is not yet fully understood, there is a lot of thinking about it that is shaped by general ideas rather than facts. In the medical literature, there are several ideas about depression that seem to be shaped by analogies to other conditions. The ways in which better understood conditions work, seems often to shape the ways in which people strive to understand more mysterious conditions such as major depression. In a recent paper, I have sought to describe eight such models. Since they are ideas that are usually based more on analogy than solid evidence, it is perhaps fair to call them "metaphors" rather than models or theories. Here is my list of eight such metaphors:

(1)  as chemical imbalances (e.g., a presumed or theoretical imbalance of normally balanced neurotransmission in the brain).

(2) as degenerative conditions (e.g., a brain disease characterised by atrophy of specified brain structures).

(3) as toxicological syndromes (a result of exposure to a noxious psychological environment, e.g. "toxic stress").

(4) Injuries (e.g., externally induced brain damage related to damaging stressors).

(5) deficiency states (e.g., a serotonin deficiency).

(6) an obsolete category (e.g., similar to obsolete terms such as 'consumption' or 'dropsy').

(7) a medical mysteries (e.g., a condition poised for a paradigm-shifting breakthrough).

(8) or evolutionary vestiges (residual components of once adaptive mechanisms have become maladaptive in modern environments).

Each of these possibilities may have elements of truth within them and may ultimately blossom into full-fledged theories capable of effectively structuring knowledge. However, for now it is important to remember that the biomedical "pedigrees" of such ideas may provide them with more weight than they really deserve.