Sex drive
Animal studies
ECS involvement
In rats AEA can transform non-copulating males into copulating males provided this is followed by sexual contact involving intromission. This transformation requires CB1 activation and is mediated by the central nervous system. Presumably AEA lifts the incapacity of non-copulating males to initiate sexual activity (Canseco-Alba and Rodríguez-Manzo, 2018).
In male rats both AEA and 2AG were found to interact with the dopaminergic system to reverse sexual inhibition (induced by copulation to satiety) and thus to modulate/increase sexual motivation (Canseco-Alba and Rodríguez-Manzo, 2019).

Plant cannabinoids
In late-proestrous female rats placed in a vaporization chamber, vaporizing 200 or 400 mg cannabis (18% THC, no CBD) generally increased signs of sexual receptiveness (Mondino et al., 2019). Although inconsistent or contradictory results between the two doses were interpreted as ‘complex modulation of sexual behavior’ it must be noted that the used doses were incredibly high, comparable to a human smoking 100 or 200 joints. However, in virgin mice oral THC inhibits female receptiveness (25 mg/kg THC and 75 mg/kg extract). As both studies use very high amounts of THC and have contradictory results it should be concluded that the effect of THC on female receptiveness is uncertain.

Human studies
ECS involvement
In male and female volunteers, masturbation to orgasm was found to increase plasma 2AG levels but not AEA, OEA, PEA or AA levels, suggesting 2AG has a role in the sexual arousal reward mechanism (Fuss et al., 2017).

Plant cannabinoids
A survey among 216 cannabis users suggests cannabis affects sexual experience: 112 (52.3%) said they used cannabis to alter their sexual experience. Eighty-two participants (38.7%) said sex was better, 34 (16.0%) said it was better in some ways and worse in others, 52 (24.5%) said it was sometimes better, and only 10 (4.7%) said it was worse. Of 202 participants, 119 (58.9%) said cannabis increased their desire for sex, 149 of the 202 participants (73.8%) reported increased sexual satisfaction, 144 of 199 participants (74.3%) reported an increased sensitivity to touch, and 132 of 201 participants (65.7%) reported an increased intensity of orgasms. Out of 199 participants, 139 (69.8%) said they could relax more during sex, and 100 of 198 participants (50.5%) said they were better able to focus. Of the 28 participants who reported difficulty reaching orgasm, 14 said it was easier to reach orgasm while using cannabis, but only 10 said that sex was better (Innocenzi et al. 2019).
In a survey among 373 sexually active women 34.0% (n = 127) reported having used cannabis before sexual activity. Most women reported increases in sex drive, improvement in orgasm, decrease in pain, but no change in lubrication. After adjusting for race, women who reported cannabis use before sexual activity had 2.13 higher odds of reporting satisfactory orgasms (adjusted odds ratio = 2.13; 95% CI = 1.05, 4.35) than women who reported no cannabis use. After adjusting for race and age, women with frequent cannabis use, regardless of use before sex or not, had 2.10 times higher odds of reporting satisfactory orgasms than those with infrequent cannabis use (adjusted odds ratio = 2.10; 95% CI = 1.01-4.44). The results suggest cannabis may improve sexual satisfaction in women (Lynn et al., 2019).

Literature:
Canseco-Alba, A., and Rodríguez-Manzo, G. (2018). Sexual interaction is essential for the transformation of non-copulating rats into sexually active animals by the endocannabinoid Anandamide. Behav. Brain Res.
Canseco-Alba, A., and Rodríguez-Manzo, G. (2019). endocannabinoids Interact With the Dopaminergic System to Increase Sexual Motivation: Lessons From the Sexual Satiety Phenomenon. Front. Behav. Neurosci. 13, 184.
Fuss, J., Bindila, L., Wiedemann, K., Auer, M.K., Briken, P., and Biedermann, S.V. (2017). Masturbation to Orgasm Stimulates the Release of the endocannabinoid 2-Arachidonoylglycerol in Humans. J. Sex. Med. 14, 1372–1379.
Lynn, B.K., López, J.D., Miller, C., Thompson, J., and Campian, E.C. (2019). The Relationship between Marijuana Use Prior to Sex and Sexual Function in Women. Sex. Med.
Mondino, A., Fernandez, S., Garcia-Carnelli, C., Castro, M.J., Umpierrez, E., Torterolo, P., Falconi, A., and Agrati, D. (2019). Vaporized Cannabis differentially modulates sexual behavior of female rats according to the dose. Pharmacol. Biochem. Behav. 172814.
Wiebe, E., and Just, A. (2019). How Cannabis Alters Sexual Experience: A Survey of Men and Women. J. Sex. Med.