East Asian Arch Psychiatry 2011;21:28-31

ORIGINAL ARTICLE

Dr Alan Tang, MBBS, FHKAM (Psychiatry), Department of Psychiatry, Prince of Wales Hospital, Hong Kong SAR, China.
Dr Rachel Yau-kar Cheung, FHKAM (Obstetrics and Gynaecology), Department of Obstetrics and Gynaecology, Prince of Wales Hospital, Hong Kong SAR, China.
Dr HJ Liang, MPhil, Department of Psychiatry, Chinese University of Hong Kong, Hong Kong.
Prof GS Ungvari, MD, PhD, The University of Notre Dame Australia / Marian Centre, Perth, Australia.
Dr Wai-kwong Tang, MBChB, MD, FHKAM (Psychiatry), Department of Psychiatry, Chinese University of Hong Kong, Hong Kong SAR, China.

Address for correspondence: Dr Wai-Kwong Tang, Department of Psychiatry, 7/F, Shatin Hospital, 33 A Kung Kok Street, Ma On Shan, New Territories, Hong Kong SAR, China.
Tel: (852) 2636 7754; email: tangwk@cuhk.edu.hk

Submitted: 22 June 2010; Accepted: 27 August 2010

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Introduction

In recent years a change in the pattern of drug abuse has been observed in Hong Kong. There has been a gradual increase in the preference for psychotropic drugs (ketamine, ecstasy, methamphetamine, triazolam / midazolam / zopiclone, cannabis, cocaine, cough mixtures, and solvents) and a simultaneous decline in the use of opiates, particularly in the young. According to the Central Registry of Drug Abuse (CRDA) of the Narcotics Division, Security Bureau, heroin is used much less frequently than psychotropic drugs.¹ Ninety eight percent of substance abusers under 21 years admitted were using psychotropic drugs; only about 3% reported heroin use.² 

Several American and European studies^3-6 have found a high rate of psychiatric co-morbidity in substance abusers. Externalising disorders are very common in adolescents,⁷ whereas in adults, depression, anxiety, and post-traumatic stress disorders are more common.^8,9 In the National Co- morbidity Survey in the US, the odds ratio for the 12- month co-occurrence of any affective disorder with drug dependence was 3.9, and the corresponding figure for any anxiety disorder was 3.6.¹⁰

Relatively little is known about the psychiatric co-morbidity of substance abusers in Hong Kong. In a local survey of over 3300 subjects, 35% with generalised anxiety disorder also suffered from co-morbid substance misuse.¹¹ In a 2005 study of 95 ketamine abusers recruited from nightclubs and drug counselling centres, 26% had lifetime psychiatric diagnoses and substance use disorders. The 2 most common diagnoses were depressive disorder (13%) and drug-induced psychotic disorder (6%).¹² Data on subjects treated in residential drug treatment centres in Hong Kong are lacking.

In overseas residential treatment centres, clinically significant depression was noted in over 50% of substance abusers using the Beck Depression Inventory¹³ and the Patient Health Questionnaire.¹⁴ In these overseas studies, the subjects mostly abused alcohol (44%), cocaine (11%) or both (31%), which was a pattern that differed from local drug abuse. As untreated psychiatric disorders worsen drug dependence treatment outcomes, the early identification and treatment of psychiatric disorders should be a priority¹⁵ in general and residential substance abuse facilities.^16,17

The pattern of drug abuse and its clinical characteristics differ to some extent depending on gender. More women than men abuse ketamine, methamphetamine, ecstasy, and hypnotics.¹⁸ Up to 42% of women take their first drug before 16 years old, whereas the corresponding figure for men is 39%.¹⁹ Female drug abusers also have a higher rate of morbidity, attain lower education levels, and enjoy poorer social support.²⁰ The common reason for women starting drug abuse is self-medication to cope with problems in life.²¹ Gender disparities in substance abuse have been increasingly studied worldwide,²⁰ but studies in Hong Kong are lacking.

The aim of this study was to describe the demographic characteristics, pattern of drug abuse, and type of psychiatric co-morbidity in female substance abuse patients treated in a residential setting.

Methods

Subjects

Subjects were recruited between November 2009 and February 2010 from a local residential detoxification centre for female substance users run by the Society for the Aid and Rehabilitation for Drug Abusers (SARDA) in Hong Kong. This non-governmental welfare organisation, established in 1961, provides free drug treatment and rehabilitation service. The typical rehabilitation programme consists of 6 to 18 months at the residential treatment centre, followed by 3 to 6 months at a halfway house.

The study protocol was approved by the Chinese University of Hong Kong – New Territories East Cluster Clinical Research Ethics Committee. Every subject signed a consent form. Consent was also obtained from the parent or guardian if the subject was under the legal age of 18 years. Patients were initially approached by an SARDA doctor, who explained the nature of the study. A patient became a study subject if she had ever used ketamine on a voluntary basis. No data were available on the reasons for their refusal.

Assessment

All psychiatric interviews were conducted by the principal author. The subjects’ age, marital status, education level, occupation, history of drug-related offences, duration of stay at the centre, and legal status (i.e. if they were under a probation order) were recorded.

Regarding substance abuse, the following information was collected: age at first contact with the substance, duration of substance abuse, types of illicit substances ever tried, and a detailed history of the pattern of substance use. Each subject’s history of psychiatric disorders and their treatment were also recorded.

The subjects were interviewed using the locally validated Chinese version of the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders-IV (C-SCID).^22,23 The C-SCID has been shown to have good inter-rater reliability, with a kappa of 0.76 for mood disorder, 0.75 for schizophrenia and other psychotic disorders, and 0.81 for anxiety disorders.^20,21

Statistical Analyses

The data were analysed using the Statistical Package for the Social Sciences, Windows version 15.0. Socio-demographic variables, patterns of drug abuse and psychiatric disorders were described with frequencies and percentages.

Results

Socio-demographics

Of 42 potential subjects, 32 agreed to participate in the study. Their mean ± standard deviation (SD) age was 20 ± 3 (range, 13-27) years; 94% were single, 3% were married, and 3% were divorced. Before admission to SARDA, 72% were employed as service workers, mostly in the catering business or as sales; 13% were students, 9% were unemployed, and 6% were clerical workers. Their mean (SD) years of education was 10 ± 1 (range, 7-11) years. Twenty nine (91%) had a history of drug-related offences.

Of these 32 subjects, 30 (94%) were admitted to the treatment centre under a probation order from the court, and only 2 (6%) were admitted voluntarily. The mean (SD) length of stay at the centre was 207 ± 125 (range, 14-480) days, and the mean (SD) age when substance abuse started was 15 ± 2 (range, 11-19) years. The mean (SD) duration of substance abuse was 5 ± 3 (range, 2-12) years. Four (13%) of the subjects were known to mental health services for a mean (SD) of 2 ± 2 (range, 1-5) years; 2 of these 4 subjects had previously been treated with psychotropic medications.

Drug Use Patterns

Twenty seven (84%) of the subjects were dependent on ketamine, 12 (38%) on methamphetamine, 11 (34%) on cocaine, and 3 (9%) each on 3,4-methylenedioxymetham- phetamine (MDMA) and benzodiazepines; 5 (16%) of the subjects were polysubstance-dependent. None were dependent on cough mixtures, opiates, zopiclone or cannabis.

As for lifetime abuse of psychotropic substances, all of them reported lifetime abuse of ketamine, 26 (81%) reported use of MDMA, and 26 (81%) reported use of cocaine. Benzodiazepines (most commonly nimetazepam) were abused by 30 (94%) of the subjects. A history of cannabis and methamphetamine abuse were also common (75% and 69%, respectively). Opiates, cough mixture and zopiclone were unpopular and abused by only 1 (3%), 2 (6%) and 4 (13%) subjects, respectively.

Psychiatric Co-morbidity

Twenty one (66%) of the subjects had lifetime psychiatric diagnoses, the most common being substance-induced mood disorder (47%), followed by substance-induced psychotic disorder (16%) and specific phobias (13%). Of the 15 subjects found to be suffering from substance-induced mood disorder, 14 were depressive-typed and 1 was mixed- typed. Major depressive disorder, obsessive-compulsive disorder, and post-traumatic stress disorder were equally common at 3%.

Discussion

Overall, ketamine was the most frequently abused drug in this study. Lifetime psychiatric diagnoses were established in 66% of the subjects. The most common psychiatric diagnoses were substance-induced mood disorder, followed by substance-induced psychotic disorder.

Socio-demographic Characteristics

The mean age of first contact with an illicit drug in this study was 15 years, considerably younger than the age of 18 years indicated by the CRDA database for female drug users.²⁴ It is possible that our subjects had more severe drug dependence, given that they were in a residential drug treatment centre, which might explain the earlier onset.

In this study, 84% of the subjects were dependent on ketamine, and all of them had used the drug. In Hong Kong, ketamine was first detected by the Government’s CRDA in 1999²⁵ and in just 2 years (1999-2001), it became the most abused substance in Hong Kong.²⁶ At present, it is the drug of choice for young abusers, with 80% of abusers under 21 years having reported its consumption.²

Co-morbid Psychiatric Disorders

Psychiatric co-morbidity was much higher in our study than a previously reported local study (66% vs. 26%),¹² which suggests that women have higher co-morbidity than men. Another reason for the discrepancy between the results may be due to sampling: our subjects were from a residential detoxification centre as opposed to community-based counselling services. Similar to the previous Hong Kong survey¹² however, the most common psychiatric diagnosis encountered in our subjects was substance-induced mood disorder.

Ketamine, the drug most often abused by our subjects, has been found to have some therapeutic effect in treatment- resistant depressive disorders.^27-29 This paradox may arise because studies have only employed ketamine for 1 or 2 infusions, whereas our subjects were taking it for much longer (5 years on average) time. More studies are needed to clarify the effects of long-term ketamine use on mood.

The second most common diagnosis was substance- induced psychotic disorder. Specifically, ketamine abuse frequently results in brief, reversible psychosis in experimental conditions involving healthy volunteers ^4,30,31 and schizophrenic patients.³² Yet, little is known about the psychiatric morbidity of chronic ketamine abuse, or the type of psychopathology may ensue. The role that ketamine could play in the pathogenesis of psychoses in these subjects is obscured by their co-dependence on cocaine and methamphetamine.

Specific phobia was the third most common diagnosis. Of the 4 subjects diagnosed with this condition, 3 suffered from animal- / insect-related phobias, and the fourth had a phobia for toilet seats.

Limitations

Our study had 3 major limitations. First, a small sample size of only 32 subjects were recruited from a single residential treatment centre. Second, 30 of the subjects were under probation orders for the possession of dangerous drugs, which constitutes an important selection bias. Finally, the characteristics of the subjects who refused to be interviewed and the reasons for refusal were not recorded. It is possible that the subjects who declined to participate might have had an even higher prevalence of psychiatric morbidity; for example, a severely depressed or paranoid subject might be more likely to refuse an interview, leading to an underestimate of psychiatric co-morbidity. Further studies of the patterns of drug abuse, risk factors, morbidity and treatment outcomes of women drug abusers, involving larger samples from multiple sources and employing more rigorous designs, are needed.

Clinical Implications

Female drug abusers in Hong Kong have particularly high psychiatric co-morbidity. Screening female drug abusers to facilitate early identification for psychiatric disorders, particularly depressive disorders and their treatment is highly recommended, as it could lead to better outcomes for these patients.

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