Suicide, induced by depression is the 11th leading cause of death (2/3 of the suicides are done by depressed patients - Cassano and Fava 2002). Many times if you don’t make it into the top 10 you are forgotten about, ignored - much like Google search results.
Maybe we should pay more attention. If a brain hack (treatment) can be developed to reduce depression and suicide the world would be a better place.
Major depressive disorder (aka: clinical depression, major depression, unipolar depression, or unipolar disorder (as defined by wiki):
is a mental disorder characterized by a pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities.
Depression cost to the individual:
Major depressive disorder (MDD) over a lifetime effects 13.3 - 17.1 % of USA and Europe citizens (Cassano and Fava 2002). The prevalence of the disorder at any one time is in the range of 2.3 to 4.9% of the population. Approximately 20% of people with recurrent depression attempt suicide. Suicide, as mentioned above is the 11th leading cause of death and represents 1.3% of all deaths (diseases of the heart 26.6%, cancer 22.8%). And you might say 1% is not much - but there is also the number of lost years due to the disease (see below). People living with depression are not usually functioning at their normal level - and hence lose many years of ‘life’.
Depression cost to society:
In the USA depression cost society 43.7 billion dollars (Cassano and Fava 2002) (could be higher now). 1.5 million disability-adjusted life years are lost each year in the world (based on 1990 data). This measurement could be put in both the individual and society cost category.
In a more recent paper (Lopez et. al., 2006) they defined burden of disease by this criteria:
disability-adjusted life years (DALYs)—to quantify the burden of diseases,
injuries, and risk factors with a single currency based on
years of life lost due to premature mortality (YLL) and
years of life lived in less than full health.
Using this criteria depression is the 3rd largest disease burden in high income countries and the 7th leading disease burden in low and middle income countries. So know depression has gone from # 11 to # 3. A 3rd entry of a Google search would get noticed.
Depression reduces lifespan beyond just suicide:
Beyond the obvious and tragic increase in the loss of life by suicide in depressed patients there appears to be additional health complications. The risk of dying from cardiac mortality is 1.5 to 3.9 fold higher in depressed patients (without prior cardiac disease) compared to the general population (Pennix et. al., 2001).
In reality, when you look at all causes of death in people with depression the risk of death is increased to around 1.3 (1.0 being baseline control) (Egede et. al., 2005) (some studies find higher numbers, other find roughly the same). And it was even worse if you had depression and diabetes.
And there is a growing recognition that there is a link between depression and both diabetes and metabolic syndrome (Dunbar et. al., 2008). Who knows which way the causal arrow points - it could even be bidirectional in this case. There is even a paper that wonders if depression should be reclassified as metabolic syndrome II (McIntyre et. al., 2007).
Take home message:
Depression is the 3rd highest disease burden in developed countries - with a very high personal and societal cost.
What ever the underlying biology (which we will continue to study) - people with major depression suffer greatly and far too many of them die from suicide and other causes of death (underlying biology of depression may contribute to both).
Depression, beyond suicide appears to increase all causes of death - but we don’t really understand why or how? There are some hints regarding the relationship between depression and metabolic syndrome/diabetes - but this needs to further studied.
Can we do anything to help these people? There are the standard treatments (wiki entry) but I hope that advances are made in the very near future to bring a better life to the large numbers of people suffering from depression.
Does the link between depression and metabolic syndrome/diabetes offer any hints of future research directions? We will have to wait and see if enough researchers are willing to explore this link further.
To saving lives and lost years.