In a large online survey of 23,500 New Zealanders who used cannabis and at least one other substance in the same six-month period, substantial proportions reported that cannabis use led them to use less alcohol (60%), synthetic cannabinoids (60%), morphine (44%), and methamphetamine (40%). About seven out of ten said cannabis had no impact on their use of LSD, MDMA, or cocaine. One in five reported that cannabis led to more tobacco use. Co-use patterns varied by age, ethnicity, and lifestyle: young adults (21–35) were more likely to report reduced drinking and methamphetamine use, while Māori were more likely to report reduced use of alcohol, tobacco, methamphetamine, and LSD.
An estimated 19% of adults in Canada, the United States, Australia, and New Zealand have used psilocybin, LSD, MDMA, or ketamine at some point in their lives. Psilocybin was the most commonly used substance, with lifetime use highest in Canada (16.3%), followed by the US (13.0%) and New Zealand (12.1%), and lowest in Australia (7.8%). Among those who had ever used a psychedelic, 10-20% had asked their medical provider about medical use, and over a third of past-year users reported experiencing an adverse health effect. Past-month use was low across all countries. Consumer interest in therapeutic use has outpaced clinical trials and therapeutic provisions, and many people use these substances outside regulated pathways, which may increase the risk of adverse events.