Studies have reported an inconsistent pattern of association between PLC and major depression, sometimes an association is found, other studies find none.
PLC has long been thought to result from loss of voluntary inhibition of a postulated centre for laughing and crying in the upper brainstem . More recent authors have suggested that prefrontal cortex is involved or that lesions in the cerebro-ponto-cerebellar pathways influence cerebellar structures that adjust the expression of laughter and crying
Patients administered tricyclic antidepressants show significant improvements PLC, with no effect on coexisting depression Reports that patients show partial to full remission within a week of starting low doses of SSRI suggest that serotonergic systems are involved. By comparison, major depression does not respond to SSRIs before three to five weeks of treatment. AVP-923, a compound consisting dextromethorphan and quinidine, has also shown significant theraputic effect.