Kiwi families, communities, and especially our young people are already paying a heavy price for a culture that has grown too casual about and perhaps even normalised cannabis use. The 2020 referendum narrowly rejected legalising recreational use (50.7% against), reflecting the common-sense view of many Kiwis that normalising a mind-altering drug is not progress. Yet trends since then show why vigilance is needed.
The latest Massey University New Zealand Drug Trends Survey (NZDTS 2025) indicates that daily cannabis use among users has jumped from 39% in 2020 to 53% in 2025. Prices are falling, availability is higher than ever, and there is a shift toward vaping and edibles, making it easier and more discreet for young people to use. Medicinal cannabis prescriptions have exploded (over 380,000 products supplied in 2025), but this has blurred lines between “medical” and recreational use, with many citing medicinal reasons while patterns suggest broader normalisation.
Population data shows past-year cannabis use at around 15.6% of adults, with higher rates among Māori (33.4%) and young people. Weekly use remains a significant issue for tens of thousands of teens and young adults. This aligns with ongoing concerns in other countries about adolescent cannabis use and its impacts on the developing brain.
A wave of major new studies, led by the Adolescent Brain Cognitive Development (ABCD) Study—the largest long-term youth brain study in the United States—paints a consistent picture: cannabis use during the teenage years interferes with critical brain development, particularly in memory, thinking speed, and reward processing. It also significantly increases the risk of serious mental health disorders later in life. The ABCD findings (e.g., slower cognitive gains in users) do not stand alone. Several other major studies published or released around late 2025–early 2026 reinforce the same concerning patterns.
A recent systematic review published in Frontiers in Psychiatry (2026) examined 36 studies with over 8,400 participants. It found consistent evidence of dose-dependent brain changes in adolescents who use cannabis, such as decreased volumes in the prefrontal cortex and hippocampus/amygdala, faster cortical thinning, and white matter impairments. It also noted increased vulnerability to addiction and variable but concerning cognitive effects. Adolescent-onset use showed greater susceptibility than adult-onset use.
One of the largest US longitudinal studies on adolescent cannabis use and psychiatric disorders analysed medical records of nearly 463,000 adolescents (ages 13–17) in Northern California (study carried out by Kaiser Permanente). Teens who reported past-year cannabis use had roughly double the risk of later diagnosis with psychotic or bipolar disorders, plus significantly higher risks of depression and anxiety (adjusted hazard ratios around 1.2–2.2). Associations held after accounting for prior mental health issues and other substance use, with stronger effects in younger teens. The study positions cannabis as a risk factor (or exacerbating factor) for psychiatric disorders, not merely a result of pre-existing conditions. Authors emphasised prevention, public health messaging, and policy responses amid the expansion of legalisation.
In a 12-month longitudinal brain imaging study, regular cannabis users (adolescents and adults) showed declining activity in the ventral striatum (the brain’s key reward centre) when anticipating non-drug rewards. This dulling of natural motivational pathways might help explain the decrease in drive, focus, and enjoyment of daily pleasures with cannabis users.
Research from both cross-sectional and longitudinal studies (including ABCD) has shown that regular cannabis use during adolescence and young adulthood is associated with modest decreases in IQ (on the order of ~2 points in meta-analyses of frequent users), verbal memory, attention, processing speed, and certain executive functions. While some earlier debates highlighted temporary effects or lower-potency products, today’s high-THC products and the adolescent brain’s ongoing maturation (into the mid-20s) amplify concerns.
The effects of adolescent cannabis use can persist in some domains even after abstinence, though there is some individual variability and confounding factors (e.g., other substances, socioeconomic status). While not every user experiences severe outcomes, population-level data and dose-response patterns warrant attention from parents, educators, and policymakers, especially given the increasing availability and potency of these products.
The research is clear and consistent: high-THC cannabis today is not the “low-potency” weed of past generations. Combined with NZ’s existing youth mental health challenges, continuing down a path of liberalisation risks entrenching generational harm, poorer educational outcomes, fractured families, and higher welfare and justice costs.
Protecting our future generations is more important than ever in a world where the acceptance of drugs and their associated harms seems to be increasing, despite the growing evidence of their harms and impacts not just on individuals but on society at large. Whether it’s local trends or international evidence, they all demand that we heed the warnings and prioritise long-term societal and family well-being over short-term liberal experimentation. Parents, churches, communities, community leaders, and politicians have a responsibility to make it clear: for our young people, cannabis is not harmless recreation; it is a significant risk we cannot afford to continue to downplay or ignore.
*Written by FF staff writers*
