United States prevalence rates tend to be somewhat higher than rates in other countries. See also
Anhedonia, a symptom of dysthymia characterized by a decreased or absent ability to enjoy a sense of pleasure
Atypical depression
Blunted affect, a symptom of PTSD, schizophrenia, and ASPD involving decreased or absent emotional response
Dysphoria, a state of feeling unwell or unhappy
Epigenetics of depression
List of medications used to treat major depressive disorder or dysthymia

References
External links
NIMH Depression Page
This may happen accidentally or intentionally as a consequence of either recreational or entheogenic drug use, though many users find the side effects to be exceedingly unpleasant and not worth the recreational effects they experience. In the context of recreational use, anticholinergics are often called deliriants. Plant sources
The most common plants containing anticholinergic alkaloids (including atropine, scopolamine, and hyoscyamine among others) are:

Atropa belladonna (deadly nightshade)
Brugmansia species
Datura species
Garrya species
Hyoscyamus niger (henbane)
Mandragora officinarum (mandrake)

Use as a deterrent
Several narcotic and opiate-containing drug preparations, such as those containing  hydrocodone and codeine are combined with an anticholinergic agent to deter intentional misuse. Examples include Hydromet/Hycodan (hydrocodone/homatropine), Lomotil (diphenoxylate/atropine) and Tussionex (hydrocodone polistirex/chlorpheniramine). However, it is noted that opioid/antihistamine combinations are used clinically for their synergistic effect in the management of pain and maintenance of dissociative anesthesia (sedation) in such preparations as Meprozine (meperidine/promethazine) and Diconal (dipipanone/cyclizine), which act as strong anticholinergic agents. == References ==