Introduction

Polysubstance use among adolescents is a public health concern and remains an essential topic for practitioners and policymakers. Polysubstance use is defined as using more than one non-prescribed licit or illicit psychoactive substance either concurrently or simultaneously [1,2]. Licit psychoactive substances include alcohol and cigarette, while illicit psychoactive substances include marijuana, cocaine, heroin, lysergic diethylamide (LSD), and amphetamines [3]. The use of licit and illicit substances frequently starts among schoolchildren during adolescents. Adolescence is a period associated with the highest risk for initiation of polysubstance use, with tobacco and alcohol use usually preceding illicit drugs. Another study found that alcohol, cocaine, and marijuana were the most commonly abused substances, both alone and in combination [4]. In Southeast Asian countries, alcohol and tobacco are commonly used polysubstance among adolescents; the Philippines (10.2%) had the highest prevalence followed by Thailand (7.4%) and Malaysia (2.7%) [5]. In Malaysia, there were increased use of alcohol (8.9% to 10.2%), tobacco (11.5% to 13.8%), and also illicit drug (1.5% to 3.4%) among adolescents from the year 2012 to 2017 [6,7]. The increased availability of alcohol and cigarette in Malaysia and lack of enforcement at ground level on under-age purchases of these substances makes adolescent more susceptible to early initiation of such substances. It has been reported that cigarettes in Malaysia are easily accessible by adolescents [8]. Alcohol drinks are also readily available in a coffee shop, supermarket and sundry shop.

Polysubstance use of alcohol, drug or tobacco, in any combination, were associated with more significant morbidity and mortality risk compared to use of a single substance only [9]. Polysubstance use could increase the likelihood of physical or psychological harm [10]. The previous study on adolescents demonstrated the link between polysubstance use with negative outcomes, including smoking in adulthood [11], risky sexual behaviour [12], and substance dependence [13]. Polysubstance uses were also associated with an increased risk of adverse psychological experiences, including depression and negative social consequences [14–16]. Other than socio-economic and physical environment factors, previous literature also reported other significant factors that contributed to substance use, such as unsupportive family condition, patient-child relationship, and being raised by a single parent [17,18]. Other factors, such as loneliness, had no close friends, inadequate peer support, involved in truancy, and being bullied, can also render adolescents vulnerable to substance use [19].

Adolescence is a period of vulnerability for developing polysubstance use. Adolescents may benefit from targeted risk profiling for prevention measures. However, there has been a lack of research exploring polysubstance use in Malaysia, especially among the younger age population. Thus, this study aims to determine the prevalence of single substance user and polysubstance user and their associated factors among adolescents in Malaysia.

Material and method

Results

The demographic characteristics of survey respondents are shown in Table 1. The total number of respondents was 27,497, with an overall response rate of 89.0%. There were an almost equal proportion of male (47.8%) and female (52.2%) respondents, as well for urban (57.8%) and rural (42.2%) area. More than half of the respondents were Malay (68.1%), aged 13–15 years (62.0%), and had parents who were married/living together (84.0%).

Table 1

Socio-demographic characteristic of school-going adolescents in Malaysia (n = 27497).

Socio-Demographic	n (%)
Gender
Male	13135 (47.8)
Female	14362 (52.2)
Age group
13–15 years	17042 (62.0)
16–17 years	10455 (38.0)
Locality of School
Urban	15899 (57.8)
Rural	11598 (42.2)
Ethnic
Malay	18713 (68.1)
Chinese	4100 (14.9)
Indian	1428 (5.2)
Other Bumiputeras	3256 (11.8)
Marital Status of Parents
Married and living together	22629 (84.0)
Divorced/Widowed/Separated	4302 (16.0)

The prevalence of substance use is shown in Table 2. The most common current substance use was tobacco (15.9%). The overall prevalence of single and polysubstance use was 17.2% (95% CI: 16.30, 18.20) and 5.1% (95% CI: 4.34, 5.96), respectively (Table 3). In general, substance use was significantly higher among males than females. For adolescent males, the most commonly used substances were smoked tobacco while for females, alcohol is the most commonly used substance. The combination of tobacco and alcohol is the most common pair of substance use among adolescents in Malaysia [(2.0 (1.66, 2.51)].

Table 2

The lifetime and current prevalence of substance use among school-going adolescents in Malaysia.

Substance use	Total	Male	Female
	% (95% CI)	% (95% CI)	% (95% CI)
Smoked Tobacco
Lifetime use	21.4 (20.04, 22.84)	34.3 (32.09, 36.55)	8.7 (7.71, 9.88)
Current use	15.9 (14.72, 17.26)	25.3 (23.28, 27.50)	6.7 (5.83, 7.71)
Alcohol
Lifetime use	19.3 (17.10, 21.70)	21.8 (19.30, 24.50)	16.8 (14.40, 19.50)
Current use	10.2 (9.00, 11.60)	12.8 (11.30, 14.50)	7.7 (6.50, 9.10)
Any Illicit drug use
Lifetime use	4.3 (3.64, 5.08)	6.6 (5.60, 7.80)	2.0 (1.57, 2.63)
Current use	3.4 (2.83, 4.12)	5.3 (4.47, 6.37)	1.5 (1.10, 2.12)

The analysis using complex sample design method (weighted analysis)

Table 3

Prevalence of single substance use and polysubstance use among school-going adolescents in Malaysia.

Substance use		Total	Male	Female
		% (95% CI)	% (95% CI)	% (95% CI)
Single Substance user*		17.2 (16.30, 18.20)	24.1 (22.71, 25.64)	10.4 (9.36, 11.56
	Illicit drug only	0.4 (0.25, 0.58)	0.5 (0.30, 0.78)	0.3 (0.12, 0.64)
	Tobacco only	11.2 (10.34, 12.15)	17.9 (16.33, 19.66)	4.6 (4.07, 5.18)
	Alcohol only	5.6 (4.82, 6.58)	5.7 (4.76, 6.88)	5.5 (4.66, 6.58)
Polysubstance user**		5.1 (4.34, 5.96)	7.9 (6.76, 9.26)	2.3 (1.78, 2.96)
	Illicit drug and tobacco	2.7 (2.16, 3.32)	4.3(3.53, 5.28)	1.1 (0.74, 1.52)
	Illicit drug and alcohol	2.5 (2.03, 3.19)	4.0 (3.22, 5.08)	1.1 (0.78, 1.50)
	Tobacco and alcohol	4.2 (3.55, 5.05)	6.6 (5.44, 7.88)	1.9 (1.49, 2.54)
	illicit drug, alcohol and tobacco use	2.2 (1.71, 2.79)	3.5 (2.74, 4.45)	0.9 (0.63, 1.28)

The analysis using complex sample design method (weighted analysis)

*currently use either one substance at one time

**concurrently use more than one any type of substance

The multinomial model showed that males were more likely to be substance users than females regardless of whether it was single or polysubstance use (single user OR = 3.0, poly user OR = 4.6). Those of younger age (13–15 years) had higher odds of single substance use than those of older age. However, age was not significant for polysubstance use (Table 4).

Table 4

Factor associated with single and polysubstance use among Malaysian adolescent from Univariate & Multivariate Multinomial Logistic Regression analysis (n = 25, 975).

	Predictive factors	Complex Sample Univariate Multinomial logistic regression (Crude Odd Ratio, OR)				Complex Sample Multivariate Multinomial logistic regression (Adjusted Odd Ratio, OR)
		Single substance use vs Non-user		Polysubstance use vs Non-user		Single substance use vs Non-user		Polysubstance use vs Non-user
		Crude OR (95% CI)	p value	Crude OR (95% CI)	p value	Adjusted OR (95% CI)	p value	Adjusted OR (95% CI)	p value
Sex
	Female	1		1		1		1
	Male	2.98 (2.59, 3.43)	<0.001	4.43 (3.39, 5.78)	<0.001	2.95 (2.57, 3.36)	<0.001	4.60 (3.59, 5.90)	<0.001
Age
	16–17 years	1		1		1		1
	13–15 years	1.36 (1.18, 1.56)	<0.001	0.87 (0.65, 1.16)	0.349	1.45 (1.29, 1.64)	<0.001	1.07 (0.83, 1.37)	0.605
Ethnic
	Malay	1		1		1		1
	Chinese	2.00 (1.71, 2.33)	<0.001	2.19 (1.58, 3.03)	<0.001	2.02 (1.72, 2.37)	<0.001	2.41 (1.75, 3.04)	<0.001
	Indian	1.05 (0.88, 1.26)	<0.580	5.12 (3.34, 7.84)	<0.001	1.00 (0.76, 1.29)	0.993	4.37 (2.92, 6.54)	<0.001
	Other Bumiputeras	1.58 (1.30, 1.92)	<0.001	4.31 (3.12, 5.95)	<0.001	1.68 (1.36, 2.09)	<0.001	5.26 (3.63, 7.52)	<0.001
Locality of School
	Urban	1		1
	Rural	0.99 (0.86, 1.15)	0.918	1.42 (0.96, 2.09)	0.075	-	-	-	-
Marital Status of Parents
	Married and living together	1		1		1		1
	Divorced/Widowed/Separated	1.26 (1.11, 1.41)	<0.001	1.87 (1.54, 2.28)	<0.001	1.21 (1.06, 1.37)	0.004	1.43 (1.13, 1.82)	0.003
Truancy in the past 30 days
	No	1		1		1		1
	Yes	1.91 (1.73, 2.11)	<0.001	4.52 (3.80, 5.38)	<0.001	1.74 (1.57, 1.93)	<0.001	3.60 (3.01, 4.30)	<0.001
Peer support
	Adequate	1		1		1		1
	Inadequate	1.70 (1.55, 1.86)	<0.001	2.00 (1.72, 2.33)	<0.001	1.25 (1.14, 1.38)	<0.001	1.36 (1.13, 1.68)	0.002
Parental or guardian bonding
	Adequate	1		1		1		1
	Inadequate	1.65 (1.52, 1.77)	<0.001	2.19 (1.88, 2.54)	<0.001	1.43 (1.31, 1.56)	<0.001	1.83 (1.50, 2.23)	<0.001
Parental or guardian never/rarely respect for privacy
	Yes	1		1
	No	1.19 (1.07, 1.32)	0.001	1.99 (1.70, 2.33)	<0.001	-	-	-	-
Anxiety
	No	1		1
	Yes	1.15 (1.05, 1.26)	0.002	2.95 (2.36, 3.68)	<0.001	-	-	-	-
Stress
	No	1		1
	Yes	1.25 (1.08, 1.45)	0.003	3.24 (2.61, 4.03)	<0.001	-	-	-	-
Depression
	No	1		1		1		1
	Yes	1.61 (1.44, 1.79)	<0.001	5.37 (4.09, 7.07)	<0.001	1.41 (1.31, 1.56)	<0.001	3.19 (2.55, 3.98)	<0.001
Loneliness
	No	1		1
	Yes	1.08 (0.94, 1.24)	0.282	2.32 (1.88, 2.86)	<0.001	-	-	-	-
Had Close friend
	Yes	1		1		1		1
	No	1.71 (1.38, 2.12)	<0.001	4.85 (3.39, 6.94)	<0.001	1.33 (1.04, 1.72)	<0.001	2.73 (1.83, 4.06)	<0.001
Being bullied
	No	1		1		1		1
	Yes	1.59 (1.42, 1.79)	<0.001	6.07 (4.91, 7.50)	<0.001	1.33 (1.04, 1.72)	<0.001	3.44 (2.83, 4.18)	<0.001

*Multinomial Logistic Regression using complex sampling design was applied.

The Complex Sample Enter method was used for variable selection. Interactions were checked and not reported. Overall fit the model for each binary logit was checked accordingly: Correctly weighted classified table (logit function 1 = 82.1%, logit function 2 = 94.7%), Weighted Area under ROC curve (logit function 1 = 71.6%, logit function 2 = 87.4%). The model was considered fit based on the classification table and area under the ROC curve

This study also showed a higher likelihood of single or polysubstance use among other Bumiputeras (single user OR = 1.7, poly user OR = 5.3), Indian (poly user OR = 4.4), and Chinese (single user OR = 2.0, poly user OR = 2.4) as compared to Malay. Those who lived with divorce/widower/separated parents also show a higher likelihood of being single substance users and polysubstance users (single user OR = 1.2, poly user OR = 1.4) compared to those who lived with both parents (Table 4).

Other associated factors for single and polysubstance use include played truant (single user OR = 1.7, poly user OR = 3.6), being bullied (single user OR = 1.3, poly user OR = 3.4), lack of peer support (single user OR = 1.3, poly user OR = 1.4), inadequate parental bonding (single user OR = 1.4, poly user OR = 1.8), had depression (single user OR = 1.4, poly user OR = 3.2) and had no close friend (single user OR = 1.3, poly user OR = 2.7) (Table 4).

Discussion

Substance use has been a matter of concern throughout the world, especially substance use among adolescents. Understanding the pattern of substance use among adolescents is vital to creating the most suitable prevention, intervention, and harm reduction strategies. The prevalence of polysubstance use in this study (5.1%) was lower compared to the United States (7.6%) [23]. Alcohol and tobacco were the most common pair of substances used. In the United States, the most frequently paired polysubstance uses were alcohol and marijuana [5]. In contrast, in the South-east Asia region [4] and other countries [24–27], smoking and consuming alcohol were common co-occurrence of substance use among adolescents. A systematic review of polysubstance use among adolescents shows that the most common polysubstance use was alcohol, tobacco, and marijuana [27].

Like other countries, male adolescents in Malaysia showed higher prevalence [4,24] and higher odds [1,28,29] for polysubstance use than females. Johnson et al. reported that males are prone to use substances as they had more curiosity and desire for adventure as these substances give them a feeling of excitement [30]. The peer influence factor and awareness of harmful substance use also contributed to the differences in substance use among gender [31]. However, it is contrary to the studies from Korea and European countries, which reported a similar prevalence of polysubstance use between males and females [32,33].

Higher age was frequently associated with polysubstance use [34–36]. However, in this study, age was only significant on single substance use but not for polysubstance use. We found that the younger age group (13–15 years) were more likely to engage in single substance use and smoking was the commonest among them. Such finding could be due to economic factors as cigarettes are the cheapest substance and easiest to access. This finding is in line with studies by Lim et al. [37] and Hammod et al. [8], where Malaysian adolescents started smoking at the young age of 14 years old. The accessibility of substances plays a vital role in initiating a single substance among the younger generation. The majority of adolescents smokers reported that it was easy to get cigarettes in Malaysia [8], and most of them were able to buy cigarettes by themselves [8]. Early initiation of smoking among younger age is a massive concern as some studies indicating that cigarettes are a gateway to other substance use such as alcohol and illicit drug [38,39].

Some studies reported that ethnic background was associated with substance use [23,40,41]. In this study, the “other Bumiputeras” group, which included Indigenous people of Sabah and Sarawak had the highest likelihood of being a polysubstance user. Culture and practice of respective ethnic groups could have played a vital role in substance use among adolescents. For example, the “other Bumiputera” group, which includes indigenous people from Sabah and Sarawak, consumes alcohol during the festive and social gatherings as culture and social obligation [42]. In contrast, all Malaysian Muslims are forbidden from drinking alcohol, and it is also illegal to sell liquor to a Muslim in Malaysia. Similarly, a study from Netherland found low consumption of alcohol use among students from a Muslim background [43]. A study by Brown et al. shows religiosity has consistently been associated with a lower level of alcohol consumption and marijuana use among adolescents [44]. Further research should be conducted to investigate factors related to ethnic variation, religion and culture on a combination of substance use among the adolescent.

Truancy and being bullied increased the odds of an adolescent in Malaysia to become polysubstance users by three times. It is similar to previous studies in the United States and Taiwan [44–47]. According to Henry et al., truancy is associated with increased odds of substance use initiation and leads to substantial escalating of substance use [48]. Truant adolescents tend to skip school in pairs or groups with mutual delinquent peers, which could lead them to substance use. Unsupervised time spent with friends during truancy increased risk for substance use which could ultimately result in an escalation of substance use [49]. An adolescent who were being bullied often experience anxiety and social concern, which could lead them to use a substance to reduce their symptoms. According to Durand et al., students who were being bullied may use a cigarette or other substances to reduce anxiety and increase their social image among peers [50]. However, further research is needed to fully understand why truancy and being bullied increase the risk of polysubstance use.

The epidemiological and clinical studies reported that substance use disorder is often associated with depression and vice versa [51,52]. This study suggested that having depression increased the odds of polysubstance use among students which is consistent with findings in the United States by Maslowsky et al. and Kelder et al., [53,54]. Depressed adolescents may “self-medicate” with tobacco, alcohol, or drugs to reduce their depression or other psychological stress. However, our finding warrants continued research to understand the nature of causal possibility between depression and substance, which may affect the intervention method for substance use among adolescents.

This study also found that a lack of protective factors such as peer support, parental bonding, and close friends increased odd of polysubstance use. An adolescent with these protective factors tends to have low risk-taking behaviour, high social bonding and gets involved with conventional peers [44]. Our study also shows that adolescents belonging to divorced or separated parents had increased odd of polysubstance use. Similar to the research done by Arkes et al., adolescents with divorced parents tend to use alcohol and marijuana [17].

Conclusion

In summary, this study found many significant factors which were associated with substance use among adolescent. These findings could have substantial implications for its prevention strategies. Targeting high-risk groups is crucial for developing effective prevention and intervention strategies. School programs to create awareness on the dangers of substance use is essential and need to be targeted at males and younger age groups. According to Tan et al. existing drug education program in Malaysia such as Tunas, PINTAR (Program Intelek Asuhan Rohani) and PIP (Program Intervensi Pelajar) need to be revised as the number of substance use among adolescent in Malaysia keeps increasing over the years [55].

The gateway drug theory suggests that using one “softer” substance, such as tobacco and alcohol, can lead to the use of another “harder” substance, such as illicit drugs. Much attention needs to be given to prevent any “soft” substance initiation, especially at a young age. Tobacco, alcohol and illicit drugs control programs should focus on restricting adolescent access to such substances. Some recommended measures include increased fines and even revoking the license of those found to be selling these products to underage individuals. Increasing tobacco duty tax, creating effective media campaigns, and formulating comprehensive strategies on specific prevention and cessation programs are equally essential. Various innovative efforts need to be taken to prevent adolescents from any substance use as it has no proven benefits in the short or long term but only known to be detrimental in many ways.