In this patient, the diagnosis of substance-induced psychotic disorder could be made as his symptoms began after cannabis use, without evidence of other substance abuse, and his urine immunoassay was positive for delta-9-tetrahydrocannabinol (Δ⁹-THC), as well as from the resolution of psychotic symptoms within 4 weeks after abstinence [7]. To date, the 2019 Annual Report of the American Association of Poison Control Centers reported that patients using cannabinoids and analogues account for 0.8% of fatalities among all substance-exposed fatalities [8]. The Oregon/Alaska Poison Center also reported that routes of cannabis exposure were ingestion (73.9%), inhalation (22.5%), topical/parenteral/rectal (0.8%), and unknown/other (2.8%) between 2015 and 2017. Most of the patients were male, and two-thirds among the overall age group were intentional use [9].

Cannabis use was reported to increase the risk of psychosis, loss of insight, and thought disorder leading to unexpected behavior, including in patients with no previous psychiatric disorders, as seen in our patient [10–12]. The severity of psychosis depends on the amount of THC [13]. THC, consumed by smoking cannabis, is one of the primary cannabinoids producing psychoactive effects through the dopaminergic pathway [14]. Over time, the concentration of THC in illegal cannabis samples has increased from less than 4% to more than 12%, suggesting a need for stricter regulation as a higher THC concentration is associated with more adverse effects [2].

Self-amputation of the penis due to cannabis-induced psychosis, as in our patient, is a devastating event that interferes with the quality of life, such as urination dysfunction or sexual function. Although psychosis is a manifestation in cannabis users, the method of self-amputation of the penis in cannabis-induced psychosis varies. Khan et al. reported a case of self-amputation of the penis in a patient with cannabis-induced psychosis whose penis was chopped off by a sharp object [6]. On the other hand, in our patient, the penile skin was trimmed several times and then completely amputated using scissors. Several times of trimming rather than stopping after the first trimming indicated the calm self-harm and persistence due to psychosis. After self-amputation in our patient who denied previous personal hygiene neglect and antisocial behavior, the amputated distal part of the penis was contaminated with ants. Although self-neglect is a finding in some substances such as methamphetamine [15], we could not determine if discarding of the amputated part of his penis was related to a cannabinoid effect leading to self-neglect or his intention to eradicate the origin of pain at the penis.

From our patient’s history of penile erection with persistent sharp pain, priapism could also be suspected in our patient. Priapism is a condition where the penis remains erect for at least 4 hours, without sexual stimulation [16]. However, our patient’s condition did not fulfill priapism diagnostic criteria because the penis was cut off before the erection exceeded 4 hours. Sickle cell disease as a priapism risk factor is a rare disease in our patient population, and his blood investigations did not demonstrate anemia [17]. Although there are some previous case reports about cannabis use and priapism, the reported patients used cannabis combined with other substances. Evans et al. reported concurrent cannabis, steroid, and cocaine use in an insulin-dependent diabetes mellitus patient [18]. Tran et al. reported a patient with priapism after use cannabis and ecstasy. It could be the interaction between cannabis and ecstasy via ecstasy stimulating dopamine release in the brain. Synergistic interactions between ecstasy and cannabis might be possible [19]. In an animal model, dopamine receptor agonist increases central oxytocinergic neurotransmission and facilitates penile erection [20]. Therefore, cannabinoid use promoting dopaminergic pathway might play a role in penile erection [19]. Moreover, cannabinoids block the thoracolumbar sympathetic pathway, which could result in the penis being unable to detumescence and increasing the risk of priapism [17, 21]. THC interacts with a cannabinoid type 1 (CB1) receptor in the central nervous system (CNS), peripheral nervous system, and vasculature. Consequently, cannabinoids might potentiate vascular effects and lead to penile erection and priapism [17, 19]. Although SR 141716A is a CB1 receptor antagonist, it increases the glutamic acid and also activates the oxytocinergic neurons, leading to penile erection in the rat model [22]. Recently, a previous case report suggested a relationship between cannabis use alone and priapism. However, the patient smoked cannabis for the previous 6 months and no self-harm or psychosis occurred [17]. Although priapism is a painful event, self-amputation is rare in a patient with normal judgement. Thus, self-harm of our patient could be the effect of psychosis.

Acute cannabis exposure has been shown to have the following effects: CNS excitation (38.3%), CNS depression (24.4%), cardiac problems (14.6%), nausea and vomiting (9.5%), unusual/unexpected subjective sensation (strange, weird, bizarre) (3.6%), abdominal pain (2.4%), and psychosis (1.6%) [9]. Our patient also felt a severe persistent sharp pain in the penis after cannabis exposure. It might be an unusual/unexpected subjective sensation from the cannabis effect. However, we could not conclude that our patient’s sharp pain was because of priapism or an unusual/unexpected subjective sensation from cannabis exposure.

In summary, cannabis-induced psychosis is an adverse effect of cannabis, which may lead to impaired judgement and unexpected self-harm. A multidisciplinary team approach, including a primary care physician, an emergency physician, a urologist, and a psychiatrist, is essential when dealing with a patient with cannabis-induced psychosis and a urogenital injury.