Most stress responses are tied together, at least loosely. If cannabinoid production is a UV or insect stress response, then herbivory may trigger cannabinoid production.
@LordHashington or anyone else wanting to explore the rabbit hole of plant light sensing @Ralf does a great job introducing:The green light myth: It's not 'safe' at night
Cryptochrome and phytochrome are decent search queries to dig further.
Can’t come up with any decent reason “dark” would be relevant, but that does not rule out the plant having one…
(Still wondering if @LordHashington has one too…)