Table 1 |
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Characteristics of depression and sickness behavior. |
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Clinical depression |
Sickness behavior |
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Basic symptoms |
Depressed mood most of the day Decreased interest or pleasure in almost all activities Anorexia, and/or significant weight loss or weight gain Insomnia or hypersomnia Psychomotor agitation or psychomotor retardation Fatigue or loss of energy Decreased ability to think or concentrate |
-- Disinterest in social interactions Anorexia and weight loss; no weight gain Sleepiness Reduced locomotor activity; no agitation Lethargy Failure to concentrate |
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Existential symptoms |
Feelings of worthlessness or guilt Suicidal ideation or behavior |
-- -- |
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Melancholic dimension |
A distinct quality of depressed mood (anhedonia) Non-reactivity Diurnal variation Early morning awakening Psychomotor retardation Excessive weight loss |
Reduced intake of sweetened milk (anhedonia) Behavioral inhibition -- -- Reduction of locomotor activity and exploration Important weight loss |
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Anxiety dimension |
Tension; physiological behavior; respiratory symptoms; genito-urinary symptoms; autonomic symptoms; anxious behavior at interview (general) |
Anxiety |
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Physio-somatic dimension |
Flu-like malaise; aches and pain; muscle tension (in some of the patients) |
Malaise and hyperalgesia (key symptoms of sickness) |
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Pyrexia |
Slightly increased body temperature |
Pyrexia |
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Onset Course |
Insiduous Waxing and waning or relapsing-remitting Chronic Sensitization of episodes Seasonal variation (Hypo)manic episodes |
Acute onset Acute adaptive response, maximal 19 to 43 days May be prolonged, but then is maladaptive -- -- -- |
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Pathways |
(Sub)chronic inflammation with increased PICs CMI activation Sensitization of inflammatory and CMI pathways Activation TRYCAT pathway O&NS Damage by O&NS Autoimmunity Neuroprogression |
Acute inflammation with increased PICs Activated -- Maybe activated TRYCAT pathway Unknown but probably yes -- -- -- |
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Triggers |
Multiple, not well defined Psychosocial stressors, medical inflammatory illness, neuroinflammatory disorders, inflammatory conditions |
Acute, highly defined Acute pathogens and tissue injury |
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Episodes tend to become autonomous from trigger |
Is always a response to a defined trigger |
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General |
Inflammation-related chronic progressive disorder |
Inflammation-induced adaptive behavioral response that is conserved through evolution |
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PICs' Janus-face |
Bad 'chronic' side: a chronic disorder with positive feedback loops between (neuro)inflammation and (neuro)degenerative processes |
Good 'acute' side: supports inflammation, redirects energy to immune cells, conserves energy and prevents negative energy balance, helps eradicating the trigger, and has anti-inflammatory effects |
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CMI, cell-mediated immune; O&NS, oxidative and nitrosative stress; PICs, pro-inflammatory cytokines; TRYCAT, tryptophan catabolites. |
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Maes et al. BMC Medicine 2012 10:66 doi:10.1186/1741-7015-10-66 |
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