The way depression is diagnosed needs to change radically.
That is according to the authors of a new article in the journal Brain, Behavior, and Immunity.
The current system is not coherent or plausible, they argue.
Depression is actually formed of 12 different sub-types, many of which have very different causes.
Mr Severi Luoto, study co-author, said:
“The evidence that major depressive disorder is a group of separate syndromes comes from the observations that patients not only have many hundreds of unique symptom profiles, but many of the symptoms often have opposite features such as insomnia or hypersomnia, or an increase or decrease in appetite.”
These 12 sub-types of depression are set off by:
- Infection, in which sickness behaviour to combat pathogens and parasites may lead to symptoms such as loss of appetite, sleep disturbances, anhedonia, impaired concentration.
- Long-term stress which is known to activate the immune system, causing an increase in proinflammatory cytokine levels that influence mood.
- Traumatic experience.
- Hierarchy conflict where events such as unemployment, exclusion from a social group, bullying at school or professional hierarchy conflicts may trigger a depressive episode.
- Romantic rejection.
- Postpartum events which lead to depression in 10-15% of women.
- The season, where Seasonal Affective Disorder (SAD) affects the individual at the same time each year.
- Chemicals such as alcohol and cocaine.
- Somatic diseases such as Alzheimer’s, Parkinson’s, migraine, epilepsy, stroke and traumatic brain injury.
- Starvation which is known to reduce mood and, when prolonged, can lead to apathy and social withdrawal.
Professor Markus Rantala, the study’s first author, said:
“With the help of the 12 depression subtypes, it will be easier to find more effective treatments for depression.
This is because the focus will be on treating the underlying reasons (triggers) of depression instead of merely focusing on the symptoms, which is how traditional psychiatry treats depression.
We argue that the occurrence of symptoms (or patterns of symptoms) depends on the subtype of the depressive episode.
The particular manifestation of depressive symptoms may have more to do with what triggered the depression (i.e. the proximate mechanisms) than the personality of the patient.”
Diagnosing people using these sub-types should make treatments more effective.
Professor Rantala said:
“Modern lifestyles – including a sedentary lifestyle with a diet high in energy and low in micronutrients – increase susceptibility to inflammatory dysregulation and chronic stress.
These in turn increase the amount of proinflammatory cytokines in peripheral blood, leading to low mood and sickness behaviours characteristic of depression.
If a depressive episode appears to be a response to an adverse life event, clinicians should evaluate whether the symptoms are adaptive or whether the depression episode has exacerbated into pathological depression.”
The study was published in the journal Brain, Behavior, and Immunity (Rantala et al., 2017).