Psychiatric morbidity in ketamine users attending counselling and youth outreach services

Ketamine and the neurobiology of depression: Toward next-generation rapid-acting antidepressant treatments

Ketamine has emerged as a transformative and mechanistically novel pharmacotherapy for depression. Its rapid onset of action, efficacy for treatment-resistant symptoms, and protection against relapse distinguish it from prior antidepressants. Its discovery emerged from a reconceptualization of the neurobiology of depression and, in turn, insights from the elaboration of its mechanisms of action inform studies of the pathophysiology of depression and related disorders. It has been 25 y since we first presented our ketamine findings in depression. Thus, it is timely for this review to consider what we have learned from studies of ketamine and to suggest future directions for the optimization of rapid-acting antidepressant treatment.

Ketamine: from prescription anaesthetic to New Psychoactive Substance

Discovered in the United States of America (USA) in the 1960s, ketamine was introduced as an anaesthetic drug to specifically replace phencyclidine. Briefly, the substance moved from the medical world to recreational users, since it was discovered that intense psychedelic experiences were obtained with dosages lower than those prescribed for anesthesia. At the end of the 90's, circulated in London nightclubs as a drug itself and as counterfeit 3,4-methylenedioxymethamphetamine tablets. In 1997, the Drug Enforcement Administration (DEA) alerted the United States (US) government to the increasing diffusion of ketamine in American 'clubs', and in 1999, the substance was added to Schedule III of drugs controlled by federal authorities. In 2002, ketamine epidemics moved to Europe, and the European Monitoring Centre for Drugs and Drug Addiction carried out a risk assessment monitoring of the phenomenon. An estimated ninety-nine percent of all global ketamine seizures occurred in Asia. Its growing popularity is due to the fact that this new psychoactive substance is cheaper than other stimulants such as MDMA that the amount used for recreational purposes does not cause respiratory depression and its legal use as a drug makes it widely available for a diversion towards illicit markets. Nevertheless, acute intoxication and several deaths have been related to exclusive ketamine use both in Europe and internationally. Since 2015, there has been and increasing rise of the illicit ketamine market and currently the drug is being used with unprecedented peaks and a consequent significant increase in seizures and clinical cases worldwide.

Test-retest reliability and cross-cultural applicability of DSM-5 adopted diagnostic criteria for ketamine use disorders

BACKGROUND

Despite increasing prevalence of nonmedical ketamine use globally, data on ketamine use disorders, which are classified in the DSM-5 under criteria for phencyclidine, are limited. This study assessed the reliability and applicability of DSM-based diagnostic criteria for ketamine use disorder.

METHODS

Participants who used ecstasy were recruited through the Tri-City Study of Club Drug Use, Abuse, and Dependence in St. Louis, Miami, and Sydney. Those who reported using ketamine (lifetime use >5 times) were included in these analyses (n = 205). Participants were interviewed using the computerized Substance Abuse Module for Club Drugs (CD-SAM) at baseline and 7 days later for the reliability of diagnoses and individual diagnostic criteria.

RESULTS

Overall, 29.3% met DSM-5 adopted criteria for ketamine use disorder at Time 1. Moderate to excellent test-retest reliability was observed consistently across study sites for any ketamine use disorder (κ = 0.57, Y = 0.61) and severe ketamine use disorder (κ = 0.62, Y = 0.79). Continued use of ketamine despite knowledge of physical or psychological problems was the most frequently endorsed individual criterion (59.0%), followed by reported withdrawal (30.2%) and physically hazardous use (29.8%). All individual criteria had acceptable reliability estimates (κ ≥ 0.41).

CONCLUSIONS

Diagnoses of ketamine use disorder can be reliably evaluated using this fully structured diagnostic instrument's questions and algorithm. Ketamine-related withdrawal among people who use ketamine should be re-evaluated. Considering that after-effects of this dissociative anesthetic can last for many hours, it is important to explore a different timeframe for possible withdrawal effects.

Striatal and white matter volumes in chronic ketamine users with or without recent regular stimulant use

BACKGROUND

Previous studies found enlarged striatum and white matter in those with stimulants use disorders. Whether primarily ketamine users (Primarily-K) and ketamine users who co-used stimulants and other substances (K+PolyS) have abnormal brain volumes is unknown. This study aims to evaluate possible brain structural abnormalities, cognitive function and depressive symptoms, between Primarily-K and K+PolyS users.

METHODS

Striatal and white matter volumes were automatically segmented in 39 Primarily-K users, 41 K+PolyS users and 46 non-drug users (ND). Cognitive performance in 7 neurocognitive domains and depressive symptoms were also evaluated.

RESULTS

Ketamine users had larger caudates than ND-controls (Right: 1-way-ANCOVA-p=0.035; K+PolyS vs. ND, p=0.030; Linear trend for K+PolyS>Primarily-K>ND, p=0.011; Left: 1-way-ANCOVA-p=0.047, Primarily-K vs. ND p=0.051) and larger total white matter (1-way ANCOVA-p=0.009, Poly+K vs. Primarily-K, p=0.05; Poly+K vs. ND p=0.011; Linear trend for K+PolyS>Primarily-K >ND, p=0.004). Across all ketamine users, they performed poorer on Arithmetic, learning and memory tasks, and were more depressed than Non-users (p<0.001 to p=0.001). Greater lifetime ketamine usage correlated with more depressive symptoms (r=0.27, p=0.008). Larger white matter correlated with better learning across all participants (r=0.21, p=0.019), while larger right caudate correlated with lower depression scores in ketamine users (r=-0.28, p=0.013).

CONCLUSION

Ketamine users had larger caudates and total white matter than ND-controls. The even larger white matter in K+PolyS users suggests additive effects from co-use of ketamine and stimulants. However, across the ketamine users, since greater volumes were associated with better learning and less depressive symptom, the enlarged caudates and white matter might represent a compensatory response.

Recovery of cognitive functioning following abstinence from ketamine

BACKGROUND

Acute and adverse effects of ketamine on cognitive functioning have been documented. No longitudinal study has examined whether cognitive deficits can be reversed following ketamine abstinence although it has been suggested in some cross-sectional studies. This study aimed to investigate the changes in cognitive functioning among ketamine users following a 12-week abstinence from ketamine.

METHODS

In this longitudinal study, 114 ketamine users completed clinical and cognitive assessments at both baseline and 12-week follow-up with the following instruments: Severity of Dependence Scale, Beck Depression Inventory (BDI), Anxiety Subscale of the Hospital Anxiety Depression Scale (HADSA), and a cognitive battery.

RESULTS

BDI (p < 0.001) and HADSA (p = 0.044) scores were significantly reduced at the 12-week follow-up. Significant improvements were found in Wechsler Adult Intelligence Scale (Third edition) immediate recall (p < 0.001) and delayed recall (p < 0.001) on the Rey-Osterrieth Complex Figure Test, and in delayed recall (p < 0.001), and immediate recall (p = 0.001) on the Logical Memory component of the Wechsler Memory Scale (Third Edition) at the 12-week follow-up. Participants completed the Stroop Inference Test significantly faster (p < 0.001); and required fewer number of attempts (p < 0.001) and produced fewer perseverative errors (p < 0.001) on the Wisconsin Card Sorting Test at the 12-week follow-up.

CONCLUSION

Chronic ketamine users' verbal and visual memory and executive functions improved after 12 weeks of ketamine abstinence.

Sex differences in response to ketamine as a rapidly acting intervention for treatment resistant depression

BACKGROUND

While ketamine has been increasingly studied for treatment resistant depression (TRD), the impact of sex differences on treatment outcomes has not been well studied. The objective was to ascertain whether there were differences in response to a single administration of ketamine for TRD between men and women, and between pre- and post-menopausal women.

METHODS

A randomized, double-blind, placebo-controlled trial (N = 99; N = 50 male; N = 49 female) was conducted to investigate the efficacy of intravenous ketamine versus active placebo as augmentation of antidepressant therapy for TRD. Patients were assigned to one of five arms; one-time administration of ketamine of varying doses (i.e., 0.1, 0.2, 0.5, and 1.0 mg/kg), and one group receiving active placebo (intravenous midazolam). A priori-planned analyses were conducted to compare responses between women and men, as well pre-vs. postmenopausal women.

RESULTS

Analyses demonstrated no significant differences between women and men in terms of treatment response (F(1,80) = 0.06, p = 0.80). There were no significant differences in the frequency of adverse effects (AEs) reported by those assigned to ketamine treatment groups (p > 0.21 for all AEs reported more than once), although women reported more headaches (12% vs. 6%, p = 0.30) and nausea (10% vs. 6%, p = 0.47). In comparing pre-vs. postmenopausal women, no differences in efficacy were observed (F(1,76) = 0.36, p = 0.55).

CONCLUSIONS

Results do not support differential efficacy or tolerability of ketamine for the treatment of TRD between women and men, nor based on menopause status among women. However, larger trials with these a priori aims are needed to confirm these results.

Ketamine as a rapid antidepressant: the debate and implications

Ketamine, a synthetic derivative of phencyclidine, is a commonly misused party drug that is restricted in high-income countries because of its addictive potential. Ketamine is also used as an anaesthetic in human and veterinary medicine. In the 1990s, research using ketamine to study the pathophysiology of schizophrenia was terminated owing to ethical concerns. Recently, controversy surrounding the drug has returned, as researchers have demonstrated that intravenous ketamine infusion has a rapid antidepressant effect and have therefore proposed ketamine as a novel antidepressant. This article debates the question of ketamine as an antidepressant, considering the drug's addictive potential, ethical concerns about prescribing a hallucinogen, the evidence base and motives behind ketamine trials.

Decreased Thalamocortical Connectivity in Chronic Ketamine Users

Disintegration in thalamocortical integration suggests its role in the mechanistic 'switch' from recreational to dysregulated drug seeking/addiction. In this study, we aimed to address whether thalamic nuclear groups show altered functional connectivity within the cerebral cortex in chronic ketamine users. One hundred and thirty subjects (41 ketamine users and 89 control subjects) underwent rsfMRI (resting-state functional Magnetic Resonance Imaging). Based on partial correlation functional connectivity analysis we partitioned the thalamus into six nuclear groups that correspond well with human histology. Then, in the area of each nuclear group, the functional connectivity differences between the chronic ketamine user group and normal control group were investigated. We found that the ketamine user group showed significantly less connectivity between the thalamic nuclear groups and the cortical regions-of-interest, including the prefrontal cortex, the motor cortex /supplementary motor area, and the posterior parietal cortex. However, no increased thalamic connectivity was observed for these regions as compared with controls. This study provides the first evidence of abnormal thalamocortical connectivity of resting state brain activity in chronic ketamine users. Further understanding of pathophysiological mechanisms of the thalamus in addiction (ketamine addiction) may facilitate the evaluation of much-needed novel pharmacological agents for improved therapy of this complex disease.

Reliability, convergent and structural validity and cut-off score of the Severity of Dependence Scale for recreational ketamine users

BACKGROUND AND AIMS

There is a lack of instruments for measuring ketamine substance use disorders. The aims were (i) to estimate the reliability and provide evidence of validity of the Severity of Dependence Scale (SDS) in a sample of recreational users, and (ii) propose a cut-off point to determine the presence of dependence.

METHODS

We conducted a web-based cross-sectional survey with recreational users who accessed webs related to recreational drug use and harm reduction. 264 recreational ketamine users who had taken it in the past month participated in the study. The Spanish version of the SDS was used. Information on ketamine use-related problems and ketamine use patterns was also collected.

RESULTS

The reliability estimation calculated by the Cronbach's alpha coefficient was 0.776. SDS showed evidence of convergent validity based on relationships with other variables. Two comparisons were made in this study to analyze the Receiver Operating Characteristic Curve. For frequency of use in the last month the area under curve (AUC) was 0.835 (CI=0.775-0.895) with optimal discrimination at an SDS score of 3. For having been in treatment for decreasing or quitting ketamine use the AUC was 0.902 (CI=0.840-0.963) and the cut-off point was 4. Confirmatory factor analysis showed a one-dimensional structure when Items 3 and 4 were correlated.

CONCLUSIONS

This study has provided evidence of reliability and validity of the ketamine version of the SDS for recreational users. Considering that ketamine use is linked to young people and its strong potential for causing serious impairment, a cut-off of 3 is proposed as indicative of dependence.

Profiling the psychotic, depressive and anxiety symptoms in chronic ketamine users

OBJECTIVE

Although concern about chronic ketamine abuse has grown, the characteristic symptomatology of chronic ketamine users has yet to be examined. This study aims to measure the psychotic, depressive and anxiety symptoms in chronic ketamine users.

METHODS

A group of chronic ketamine users in Guangzhou, China were evaluated. The socio-demographic and drug use characteristics of subjects were documented. Symptoms of psychosis, depression, anxiety were evaluated by the Positive and Negative Syndrome Scale (PANSS), Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI). The severity of the symptoms was identified by standard severity cutoffs.

RESULTS

The PANSS total score, positive symptom, negative symptom, general psychopathology subscale score were 45.3±8.4, 8.0±1.7, 13.2± 3.9 and 24.2± 4.9 respectively. BDI and BAI score was 13.1±6.5 and 15.7±9.6 respectively. 77.5% and 46.0% of the subjects showed moderate to severe depressive symptoms and anxiety symptoms respectively. The BDI score was positively correlated with ketamine use frequency. The BAI score was positively correlated with ketamine use frequency.

CONCLUSIONS

Depressive symptoms were commonly presented in chronic ketamine users. The higher ketamine use frequency and dosage were associated with more severe depressive symptoms.