PubMed Health⌕ Search

Biomedical subjects

Louisa Degenhardt

Publications and source records attributed to Louisa Degenhardt.

At least 19 recordsLinked to original sources
PubMed2026

Cannabis and cannabinoids for the treatment of mental and substance use disorders and symptoms: A systematic review and meta-analysis of experimental and observational studies.

BACKGROUND: Interest in cannabinoids for mental and substance use disorders is increasing. We examined experimental and observational evidence for treating these disorders and their symptoms. METHODS: Systematic review and meta-analysis (PROSPERO CRD42023467536). We searched CENTRAL, MEDLINE, Embase and PsycINFO to May 2025 for studies of cannabinoids in adults (≥18 years) with ADHD, anxiety, depression, PTSD, psychosis or Tourette syndrome, or alcohol, cannabis, opioid or tobacco use disorders. Two reviewers screened, extracted and assessed quality using a risk-of-bias tool and GRADE. RESULTS: We included 82 experimental and 118 observational studies. In RCTs, cannabinoids reduced anxiety symptoms (SMD=-0.40; 95% CI: -0.57, -0.23; I²=90%) and, in one small trial, PTSD symptoms (SMD=-2.60; 95% CI: -4.58, -0.62; n=20), with trivial-to-no effect on depression (SMD=-0.20; 95% CI: -0.43, 0.04; I²=91.6%), ADHD, psychosis and Tourette syndrome. Much anxiety and depression evidence came from symptoms measured as secondary outcomes in other primary conditions. Cannabinoids worsened cannabis use disorder severity in one RCT (SMD=2.35; 95% CI: 1.49, 3.21), with no effect on craving or withdrawal; evidence for alcohol, opioid and tobacco use disorders was very limited. Observational studies suggested improvements but had high risk of bias. The only significant safety finding was increased withdrawals due to adverse events with THC (OR=2.78; 95% CI: 1.66, 4.65). Certainty was predominantly very low. DISCUSSION: The evidence base shows very low certainty, high heterogeneity and methodological limitations, and is insufficient to support cannabinoids as first-line treatment. Signals for anxiety and PTSD are limited by indirectness and low certainty; no benefit was evident for depression; THC-related safety signals warrant careful consideration.

Humans↗
PubMed2026

Implementation factors shaping British Columbia's drug decriminalization pilot: A systematic review with narrative synthesis.

BACKGROUND: In January 2023, British Columbia (BC) became the first Canadian province to implement a legally sanctioned drug decriminalization policy, removing criminal penalties for adults possessing 2.5 g or less of opioids, cocaine, methamphetamine, and MDMA. Introduced as a three-year pilot, it aimed to reframe substance use as a public health issue, reduce stigma, and improve health and social service engagement. Criminal penalties were reintroduced for drug possession in most public spaces in May 2024, and the pilot ended in January 2026. Its termination has been interpreted as policy failure; this review aimed to examine how the pilot was implemented in practice and to identify factors that shaped its operationalization and early implementation-relevant outcomes. METHODS: We conducted a systematic review with narrative synthesis of peer-reviewed literature examining implementation-relevant aspects of BC's decriminalization pilot. Six databases were searched (January-February 2026) for studies published May 31, 2022-February 1, 2026. The protocol was registered in PROSPERO (CRD420251271694). RESULTS: Twenty-seven studies were included. Four cross-cutting implementation barriers were identified: pilot design features, public and cross-sector communication gaps, limited frontline training, and insufficient funding and infrastructure. Design features included the 2.5 g possession threshold, misalignment with real-world drug use patterns; the three-year timeframe, which constrained system-level effects; and the May 2024 amendment, which introduced additional instability. The pilot was implemented without commensurate investment in harm reduction, treatment, or housing infrastructure, within already constrained systems. CONCLUSION: BC's decriminalization pilot suggests the effects of legal reform are shaped by implementation context. Early outcomes may reflect design features, institutional readiness, and system capacity rather than legal change alone; longer-term impacts remain uncertain. Future reforms should align legal change with coordinated implementation, operational guidance, public communication, and adequate service infrastructure.

British Columbia↗
PubMed2006

Affective disorders, anxiety disorders and psychological distress in non-drinkers.

BACKGROUND: Non-drinkers have elevated levels of psychological distress but a recent study reported no elevation in prevalence of diagnosed disorders. We aimed to determine the prevalence of affective and anxiety disorders (from the CIDI-A) in current abstainers and contrast results with findings for psychological distress (K10) in the same sample. METHODS: Cross-sectional, representative household survey of adult Australians. RESULTS: Non-/occasional drinkers had higher levels of psychological distress than light drinkers, and distress in heavy drinkers was even higher. Heavy drinkers also had the highest rates of most disorders. Non-/occasional drinkers showed significantly elevated prevalence only of dysthymia, agoraphobia and posttraumatic stress disorder compared with light drinkers. LIMITATIONS: Statistical power was limited for investigating low prevalence disorders. History of alcohol consumption was not collected. The CIDI-A and K10 have finite validity. CONCLUSIONS: This study confirmed J-shaped relationships between psychological distress and alcohol consumption. Although affective and anxiety disorders also showed non-linear relationships with alcohol consumption, non-/occasional drinkers are not at increased risk for all disorders compared to light drinkers. The pattern of symptomatology in non-/occasional drinkers may be of a different character to that in heavy drinkers, as well as being less severe.

Adolescent↗
PubMed2006

Identification and quantification of change in Australian illicit drug markets.

BACKGROUND: In early 2001 Australia experienced a sudden reduction in the availability of heroin which had widespread effects on illicit drug markets across the country. The consequences of this event, commonly referred to as the Australian 'heroin shortage', have been extensively studied and there has been considerable debate as to the causes of the shortage and its implications for drug policy. This paper aims to investigate the presence of these epidemic patterns, to quantify the scale over which they occur and to estimate the relative importance of the 'heroin shortage' and any epidemic patterns in the drug markets. METHOD: Key indicator data series from the New South Wales illicit drug market were analysed using the statistical methods Principal Component Analysis and SiZer. RESULTS: The 'heroin shortage' represents the single most important source of variation in this illicit drug market. Furthermore the size of the effect of the heroin shortage is more than three times that evidenced by long-term 'epidemic' patterns. CONCLUSION: The 'heroin shortage' was unlikely to have been a simple correction at the end of a long period of reduced heroin availability, and represents a separate non-random shock which strongly affected the markets.

Amphetamine↗
PubMed2006

Posttraumatic stress disorder among female street-based sex workers in the greater Sydney area, Australia.

BACKGROUND: This paper examines rates of exposure to work-related violence and other trauma, and the prevalence of lifetime and current posttraumatic stress disorder (PTSD) among female street-based sex workers. It also investigates associations between current PTSD symptoms and: demographic characteristics, psychiatric comorbidity, injecting and sex risk behaviours, and trauma history. METHODS: Cross sectional data collected from 72 women via face to face structured interviews. The interview included structured diagnostic assessment of DSM-IV PTSD; drug dependence; depression; experience of childhood trauma; and an assessment of sex working history. RESULTS: All but one of the women interviewed reported experiencing trauma, with the majority reporting multiple traumas that typically began in early childhood. Child sexual abuse, adult sexual assault and work related violence were commonly reported. Just under half of the women met DSM-IV criteria for PTSD and approximately one-third reported current PTSD symptoms. Adult sexual assault was associated with current PTSD symptoms. Depression and drug dependence were also highly prevalent; cocaine dependence in particular was associated with elevated rates of injecting risk and sexual risk behaviours. CONCLUSION: These women reported complex trauma histories and despite ongoing opportunities for clinical intervention, they continued to experience problems, suggesting that current models of treatment may not be appropriate. More targeted interventions, and integrated mental health and drug treatment services are needed to address the problems these women are experiencing. Outreach services to these women remain a priority. Education strategies to reduce risky injecting and sexual behaviours among sex workers should also remain a priority.

Adult↗
PubMed2006

The "lessons" of the Australian "heroin shortage".

Heroin use causes considerable harm to individual users including dependence, fatal and nonfatal overdose, mental health problems, and blood borne virus transmission. It also adversely affects the community through drug dealing, property crime and reduced public amenity. During the mid to late 1990s in Australia the prevalence of heroin use increased as reflected in steeply rising overdose deaths. In January 2001, there were reports of an unpredicted and unprecedented reduction in heroin supply with an abrupt onset in all Australian jurisdictions. The shortage was most marked in New South Wales, the State with the largest heroin market, which saw increases in price, dramatic decreases in purity at the street level, and reductions in the ease with which injecting drug users reported being able to obtain the drug. The abrupt onset of the shortage and a subsequent dramatic reduction in overdose deaths prompted national debate about the causes of the shortage and later international debate about the policy significance of what has come to be called the "Australian heroin shortage". In this paper we summarise insights from four years' research into the causes, consequences and policy implications of the "heroin shortage".

Adolescent↗
PubMed2006

Using intervention time series analyses to assess the effects of imperfectly identifiable natural events: a general method and example.

BACKGROUND: Intervention time series analysis (ITSA) is an important method for analysing the effect of sudden events on time series data. ITSA methods are quasi-experimental in nature and the validity of modelling with these methods depends upon assumptions about the timing of the intervention and the response of the process to it. METHOD: This paper describes how to apply ITSA to analyse the impact of unplanned events on time series when the timing of the event is not accurately known, and so the problems of ITSA methods are magnified by uncertainty in the point of onset of the unplanned intervention. RESULTS: The methods are illustrated using the example of the Australian Heroin Shortage of 2001, which provided an opportunity to study the health and social consequences of an abrupt change in heroin availability in an environment of widespread harm reduction measures. CONCLUSION: Application of these methods enables valuable insights about the consequences of unplanned and poorly identified interventions while minimising the risk of spurious results.

Australia↗
PubMed2006

Risk and benefit perceptions of party drug use.

A cross-sectional survey of 372 regular ecstasy users was conducted to examine the benefits and risks perceived to be associated with the use of party drugs. A wide range of benefits and risks were reported across six drug types with some considered drug-specific. Commonly perceived risks included physical and psychological harms that were consistent with current harm reduction messages. Harm reduction campaigns may need to acknowledge benefits of drug use to ensure health promotion messages are considered credible and acceptable to users.

Adolescent↗
PubMed2006

Examining links between cocaine use and street-based sex work in New South Wales, Australia.

We examined potential links between cocaine use and street-based sex work in New South Wales (NSW), Australia, following reports of increased cocaine use among injection drug users (IDU). Police data on prostitution and possession/use of cocaine was analysed using time series analysis. Interviews with key informants and IDU were also conducted, and data on cocaine use from ongoing monitoring systems targeted at IDU were analysed. There was a clear increase in cocaine use among IDU which occurred in 2001. This occurred at the same time as an increase in prostitution offenses. Qualitative data suggested that a greater number of primary heroin users were engaging in street-based sex work, which was driven in part by the increases in cocaine use among this group. Subsequent reductions in cocaine availability led to decreased cocaine use and possession offenses, along with reductions in prostitution offenses.

Cocaine-Related Disorders↗
PubMed2006

Documenting the heroin shortage in New South Wales.

Australian heroin markets have recently undergone dramatic change, sparking debate about the nature of such markets. This study aimed to determine the onset, peak and decline of the heroin shortage in New South Wales (NSW), using the most appropriate available methods to detect market level changes. The parameters of the heroin shortage were determined by reviewing: reports of heroin users about availability and price (derived from the existing literature and the Illicit Drug Reporting System); qualitative interviews with injecting drug users, and health and law enforcement professionals working in the illicit drug field; and examining data on heroin seizures over the past decade. There was a marked reduction in heroin supply in NSW in early 2001. An increase in the price of heroin occurred in 2001, whereas it had decreased steadily since 1996. A reduction in purity also occurred, as reported by drug users and heroin seizures. The peak period of the shortage appears to have been January to April 2001. The market appears to have stabilised since that time, although it has not returned to pre-2001 levels: heroin prices have decreased in NSW for street grams, but not to former levels, and the price of 'caps' (street deals) remain elevated. Heroin purity in NSW has remained low, with perhaps a 10% increase above the lowest recorded levels. These data support the notion that the heroin market in NSW underwent significant changes, which appear to have involved a lasting shift in the nature of the market.

Commerce↗
PubMed2006

Changes in the initiation of heroin use after a reduction in heroin supply.

Increasing heroin use in Australia over the past 30 years has been associated with a decline in the age of initiation to heroin use. The 2001 Australian heroin shortage was used to assess the effects of a reduction in heroin supply on age of initiation into heroin injecting. Data collected from regular injecting drug users (IDU) over the period 1996 - 2004 as part of the Australian Illicit Drug Reporting System were examined for changes in self-reported age of first heroin use after the onset of the heroin shortage. Estimates were also made of the number of young people who may not have commenced injecting heroin during the heroin shortage. The proportion of IDU interviewed in the IDRS who were aged <or=24 years decreased from 46% in 1996 to 12% in 2004, with the most marked drop in 2001, the year in which there was an abrupt and marked reduction in heroin availability. Of those who reported first injecting between 1993 and 2000, similar proportions reported heroin and amphetamine as the first drug injected. After 2000, methamphetamine was the drug most often reported as being the first injected. Estimates suggested that between 2745 and 10,560 young people may not have begun to inject heroin in 2001 as a result of reduced heroin supply. If around one in four of these young users had progressed to regular or dependent heroin use, then there may have been a reduction of between 700 and 2500 dependent heroin users. There was an increase in amphetamine injecting but it is unclear to what extent any reduction in heroin injecting has been offset by increased amphetamine injecting. Reduced heroin availability probably resulted in a reduction in the number of new heroin injectors in Australia. Efforts need to be made to reduce the chances that young people who have initiated methamphetamine injecting do not move to heroin injecting when the heroin supply returns.

Adolescent↗
PubMed2006

Trends in morphine prescriptions, illicit morphine use and associated harms among regular injecting drug users in Australia.

This paper examines population trends in morphine prescriptions in Australia, and contrasts them with findings from annual surveys with regular injecting drug users (IDU). Data on morphine prescriptions from 1995 to 2003 were obtained from the Drug Monitoring System (DRUMS) run by the Australian Government Department of Health and Ageing. Data collected from regular IDU as part of the Australian Illicit Drug Reporting System (IDRS) were analysed (2001 - 2004). The rate of morphine prescription per person aged 15 - 54 years increased by 89% across Australia between 1995 and 2003 (from 46.3 to 85.9 mg per person). Almost half (46%) of IDU surveyed in 2004 reported illicit morphine use, with the highest rates in jurisdictions where heroin was less available. Recent morphine injectors were significantly more likely to be male, unemployed, out of treatment and homeless in comparison to IDU who had not injected morphine. They were also more likely to have injected other pharmaceutical drugs and to report injection related problems. Among those who had injected morphine recently, the most commonly reported injecting harms were morphine dependence (38%), difficulty finding veins into which to inject (36%) and scarring or bruising (27%). Morphine use and injection is a common practice among regular IDU in Australia. In some cases, morphine may be a substitute for illicit heroin; in others, it may be being used to treat heroin dependence where other pharmacotherapies, such as methadone and buprenorphine, are perceived as being unavailable or undesirable by IDU. Morphine injection appears to be associated with polydrug use, and with it, a range of problems related to drug injection. Further research is required to monitor and reduce morphine diversion and related harms by such polydrug injectors.

Adolescent↗
PubMed2006

Reflections on the development and implementation of an early warning system for ecstasy and related drug markets in Australia.

Regular and systematic monitoring of drug markets provides the basis for evidence-based policy. In Australia, trends in ecstasy and related drug (ERD) markets have been monitored in selected jurisdictions since 2000 and nationally since 2003, by the Party Drugs Initiative (PDI). The PDI maximises the validity of conclusions by triangulating information from (a) interviews with regular ecstasy users (REU), (b) interviews with key experts and (c) indicator data. There is currently no other system in Australia for monitoring these markets systematically; however, the value of the PDI has been constrained by the quality of available data. Difficulties in recruiting and interviewing appropriate consumers (REU) and key experts have been experienced, but largely overcome. Limitations of available indicator data from both health and law enforcement continue to present challenges and there remains considerable scope for enhancing existing routine data collection systems, to facilitate monitoring of ERD markets. With an expanding market for ecstasy and related drugs in Australia, and in the context of indicator data that continue to be limited in scope and detail, there is a strong argument for the continued collection of annual, comparable data from a sentinel group of REU, such as those recruited for the PDI.

Australia↗
PubMed2006

Alcohol use and risk taking among regular ecstasy users.

We examine alcohol use in conjunction with ecstasy use and risk-taking behaviors among regular ecstasy users in every capital city in Australia. Data on drug use and risks were collected in 2004 from a national sample of 852 regular ecstasy users (persons who had used ecstasy at least monthly in the preceding 6 months). Users were grouped according to their typical alcohol use when using ecstasy: no use, consumption of between one and five standard drinks, and consumption of more than five drinks ("binge" alcohol use). The sample was young, well educated, and mainly working or studying. Approximately two thirds (65%) of the regular ecstasy users reported drinking alcohol when taking ecstasy. Of these, 69% reported usually consuming more than five standard drinks. Those who did not drink alcohol were more disadvantaged, with greater levels of unemployment, less education, higher rates of drug user treatment, and prison history. They were also more likely than those who drank alcohol when using ecstasy to be drug injectors and to be hepatitis C positive. Excluding alcohol, drug use patterns were similar between groups, although the no alcohol group used cannabis and methamphetamine more frequently. Binge drinkers were more likely to report having had three or more sexual partners in the past 6 months and were less likely to report having safe sex with casual partners while under the influence of drugs. Despite some evidence that the no alcohol group were more entrenched drug users, those who typically drank alcohol when taking ecstasy were as likely to report risks and problems associated with their drug use. It appears that regular ecstasy users who binge drink are placing themselves at increased sexual risk when under the influence of drugs. Safe sex messages should address the sexual risk associated with substance use and should be tailored to reducing alcohol consumption, particularly targeting "heavy" alcohol users. The study's limitations are noted.

Adolescent↗
PubMed2006

Is cannabis use a contributory cause of psychosis?

OBJECTIVE: To assess whether cannabis use in adolescence and young adulthood is a contributory cause of schizophreniform psychosis in that it may precipitate psychosis in vulnerable individuals. METHOD: We reviewed longitudinal studies of adolescents and young adults that examined the relations between self-reported cannabis use and the risk of diagnosis with a psychosis or of reporting psychotic symptoms. We also reviewed studies that controlled for potential confounders, such as other forms of drug use and personal characteristics that predict an increased risk of psychosis. We assessed evidence for the biological plausibility of a contributory causal relation. RESULTS: Evidence from 6 longitudinal studies in 5 countries shows that regular cannabis use predicts an increased risk of a schizophrenia diagnosis or of reporting symptoms of psychosis. These relations persisted after controlling for confounding variables, such as personal characteristics and other drug use. The relation did not seem to be a result of cannabis use to self-medicate symptoms of psychosis. A contributory causal relation is biologically plausible because psychotic disorders involve disturbances in the dopamine neurotransmitter systems with which the cannabinoid system interacts, as demonstrated by animal studies and one human provocation study. CONCLUSION: It is most plausible that cannabis use precipitates schizophrenia in individuals who are vulnerable because of a personal or family history of schizophrenia.

Adolescent↗
PubMed2006

What are the policy implications of the evidence on cannabis and psychosis?

OBJECTIVE: To explore the implications for mental health services, for health education about the risks of cannabis use, and for public policy toward cannabis use of observational evidence that cannabis use is a contributory cause of psychosis. METHOD: Using comparative analyses of similar evidence for the harmful effects of alcohol, tobacco, and amphetamine use, we considered the relation between observational evidence and action on cannabis. We examined arguments on the grounds of public health prudence for discouraging cannabis use by young individuals. With the assumption that the relation may be causal, we considered recommendations for policy in mental health services, health education, and public policy toward cannabis. RESULTS: The observational evidence and biological plausibility of the hypothesis that cannabis is a contributory cause of psychosis is at least as strong as evidence for causal relations between heavy alcohol and amphetamine use and psychosis. On public health grounds, there is a good case for discouraging cannabis use among adolescents and young adults. It remains uncertain how best to discourage use and at whom campaigns to reduce cannabis use should be targeted. CONCLUSIONS: We should discourage young adults seeking treatment in mental health services from using cannabis and inform them of the probable mental health risks of cannabis use, especially of early and frequent use. We must exercise caution in liberalizing cannabis laws in ways that may increase young individuals' access to cannabis, decrease their age of first use, or increase their frequency of cannabis use. We should consider the feasibility of reducing the availability of high-potency cannabis products.

Canada↗
PubMed2005

Prevalence of injecting drug use and associated risk behavior among regular ecstasy users in Australia.

BACKGROUND: The aim of the study was to investigate the prevalence of injecting drug use and associated risk behaviour among a sentinel sample of ecstasy users. METHODS: Cross-sectional surveys were conducted with regular ecstasy users as part of an annual monitoring study of ecstasy and related drug markets in all Australian capital cities. RESULTS: Twenty-three percent of the sample reported having ever injected a drug and 15% reported injecting in the 6 months preceding interview. Independent predictors of lifetime injection were older age, unemployment and having ever been in prison. Completion of secondary school and identifying as heterosexual was associated with a lower likelihood of having ever injected. Participants who had recently injected typically did so infrequently; only 9% reported daily injecting. Methamphetamine was the most commonly injected drug. Prevalence of needle sharing was low (6%), although half (47%) reported sharing other injecting equipment in the preceding 6 months. CONCLUSIONS: Ecstasy users who report having injected a drug at some time appear to be demographically different to ecstasy users who have not injected although neither are they typical of other drug injectors. The current investigation suggests that ongoing monitoring of injecting among regular ecstasy users is warranted.

Adult↗