Students’ use of caffeine, alcohol, dietary supplements, and illegal substances for improving academic performance in a New Zealand university

Figures & data

Table 1. Characteristics of the sample, and comparison with University of Otago student population.

		Participants			Population
		n	%	95% CI	n	%
Gender^1
	Male	227	33	(30, 37)	8,720	42.3
	Female	458	67	(63, 70)	11,879	57.7
Age^2
	18–20	338	49	(46, 53)	9,003	43.7
	21–23	240	35	(31, 39)	5,868	28.5
	24–26	51	7	(5, 9)	1,716	8.3
	27+	56	8	(6, 10)	3,911	19.0
Ethnicity^3
	NZ European	535	78	(75, 81)	15,126	73.4
	Māori	47	7	(5, 9)	1,759	8.5
	Pacific	18	3	(1, 4)	804	3.9
	Asian	105	15	(13, 18)	3,877	18.8
	Other	36	5	(4, 7)	14,88	7.2
Course^3
	Bachelor	536	78	(75, 81)	15,105	72.1
	Undergraduate diploma	43	6	(4, 8)	47	2.1
	Postgraduate diploma/certificate	23	3	(2, 5)	1,366	6.5
	Masters	23	3	(2, 5)	1,196	5.7
	Honors	30	4	(3, 6)	431	2.1
	PhD	30	4	(3, 6)	1,328	6.3
Academic divisions^4
	Humanities	207	30	(27, 34)		26.8
	Business	83	12	(10, 15)		15.9
	Science	225	33	(29, 36)		24.0
	Health Sciences	228	33	(30, 37)		31.9
	Other	42	6	(4, 8)
Total		685			20,601

Notes: ¹2 students identified as gender diverse.

² 103 students were under the age of 18 in the student population, however would have been excluded from answering the survey questionnaire.

³ Multiple responses allowed.

⁴ Multiple responses were allowed for participants. However, population percentages are Equivalent Full-time Students per division.

Table 2. Prevalence of use by substance for improving academic performance.

Substance	Ever used			Used in the last 6 months
	n	%	95% CI	n	%	95% CI
Caffeine	479	70	(66.3, 73.3)	416	61	(57, 64.4)
Alcohol	42	6	(4.5, 8.2)	25	4	(2.4, 5.3)
Dietary supplements	218	32	(28.3, 35.5)	161	24	(20.4, 26.9)
Prescription stimulants^1	28	4	(2.7, 5.9)	11	2	(0.8, 2.9)
Other prescription substances	19	3	(2.7, 4.3)	15	2	(1.2, 3.6)
Illicit substances	28	4	(2.7, 5.9)	19	3	(1.7, 4.3)
Controlled substances^2	67	10	(7.7, 12.3)	42	6	(4.5, 8.2)
Any substance	545	80	(76.3, 82.5)	481	70	(66.6, 73.6)

Notes: ¹Excludes people with a diagnosis of ADHD.

² Prescription stimulant, other prescription substance and illicit substance combined.

Table 3. Univariate odds ratios showing relationship between demographic factors and lifetime use of substances.

	CaffeineOR (95% CI)	Alcohol OR (95% CI)	Dietary Supplements OR (95% CI)	All controlled substances OR (95% CI)
Gender
Male
Female	0.99(0.70-1.40)	0.52(0.28-0.98)	1.29(0.91-1.83)	0.32(0.19-0.54)
Age (yrs)
18-20	(ref.)
21-23	1.54(1.06-2.23)	1.73(0.87-3.44)	1.18(0.83-1.69)	1.52(0.84-2.77)
24-26	2.34(1.10-4.98)	1.71(0.55-5.34)	1.14(0.61-2.13)	2.54(1.07-6.05)
27+	0.62(0.35-1.10)	1.14(0.32-4.04)	0.91(0.49-1.70)	2.62(1.14-6.01)
Year of study
First	(ref.)
Second	1.61(1.01-2.58)	1.66(0.59-4.67)	1.05(0.64-1.70)	1.56(0.59-4.14)
Third	2.10(1.31-3.36)	1.02(0.33-3.10)	1.21(0.76-1.93)	2.10(0.84-5.24)
Fourth	2.06(1.18-3.60)	2.17(0.73-6.47)	1.18(0.68-2.03)	2.34(0.87-6.44)
Fifth	2.68(1.31-5.48)	3.38(1.09-10.55)	0.74(0.37-1.49)	4.38(1.58-12.14)
6th	2.86(0.78-10.57)	3.72(0.68-20.31)	0.57(0.15-2.12)	3.17(0.60-16.83)
7+	1.63(0.75-3.55)	1.42(0.27-7.35)	1.29(0.60-2.77)	5.88(1.97-17.52)
Subject Area^1 (multiple subject areas possible)
Humanities	1.19(0.83-1.71)	1.80(0.96-3.40)	1.07(0.75-1.52)	2.06(1.22-3.48)
Business	1.07(0.64-1.77)	1.17(0.02-1.23)	0.80(0.48-1.33)	1.21(0.57-2.55)
Sciences	0.91(0.65-1.27)	0.90(0.45-1.73)	1.23(0.88-1.71)	0.74(0.42-1.29)
Health Sci.	0.97(0.68-1.38)	0.71(0.34-1.48)	0.86(0.61-1.23)	0.57(0.30-1.06)
Competitive courses^1
Medicine	1.13(0.67-1.90)	0.80(0.28-2.30)	0.65(0.38-1.11)	1.10(0.51-2.42)
Law	1.11(0.64-1.91)	1.81(0.77-4.24)	0.96(0.56-1.63)	1.48(0.70-3.13)
HSFY	0.62(0.33-1.16)	0.70(0.16-2.98)	0.86(0.44-1.68)	no users

Note: Bolded values indicate CI does not include 1.0. All analyses include only a single predictor (e.g. gender, age, course of study).

¹ For these analyses, each subject course group was compared to all other students in separate analyses, due to potentially overlapping categories.

Table 4. Frequency of use for improving academic performance by substance.

Frequency of use (for any purpose)	Caffeine	Alcohol	Dietary supplements	Prescription stimulants	Other prescription substances	Other illicit substances
	% (95% CI)	% (95% CI)	% (95% CI)	% (95% CI)	% (95% CI)	% (95% CI)
At least once a day	32 (29, 36)	0 (0, 0)	15 (12, 18)	0 (0, 0)	1 (0, 1)	1 (0, 1)
Once a week	16 (13, 18)	1 (0, 1)	5 (4, 7)	0 (0, 0)	0 (0, 1)	1 (0, 2)
1–2 times a month	7 (5, 9)	1 (0, 2)	2 (0, 0)	0 (0, 1)	0 (0, 1)	1 (0, 1)
Less than once a month	6 (4, 7)	1 (0, 2)	1 (0, 2)	1 (0, 2)	1 (0, 1)	0 (0, 1)
Used, but not in last 6 months	10 (7, 12)	3 (2, 4)	9 (6, 11)	3 (1, 4)	1 (0, 1)	1 (0, 2)
Never used	30 (27, 34)	94 (92, 96)	68 (65, 72)	96 (95, 98)	97 (96, 98)	96 (95, 98)

Table 5. Perceptions of safety and morality of substances for improving academic performance.

	Strongly agree	Agree	Neither agree nor disagree	Disagree	Strongly disagree
	% (95% CI)	% (95% CI)	% (95% CI)	% (95% CI)	% (95% CI)
Safety
Use of caffeine is safe	23 (19, 26)	57 (53, 60)	16 (13, 19)	4 (3, 6)	1 (0, 2)
Use of dietary supplements is safe	24 (21, 28)	43 (39, 46)	28 (25, 32)	4 (2, 5)	2 (1, 3)
Use of prescription stimulants is safe	2 (1, 3)	10 (8, 12)	33 (29, 36)	34 (30, 37)	22 (19, 25)
Use of other prescription substances is safe	0 (0, 1)	4 (2, 5)	30 (27, 34)	35 (31, 38)	31 (28, 35)
Use of illicit substances is safe	0 (0, 1)	2 (1, 4)	12 (10, 15)	23 (20, 26)	62 (59, 66)
Morality
Use of caffeine is moral	38 (35, 42)	42 (38, 46)	16 (13, 19)	2 (1, 4)	2 (1, 3)
Use of dietary supplements is moral	35 (31, 38)	38 (35, 42)	22 (19, 25)	3 (2, 5)	2 (1, 3)
Use of prescription stimulants is moral	5 (3, 7)	8 (6, 11)	24 (21, 27)	29 (26, 33)	34 (31, 38)
Use of other prescription substances is moral	4 (3, 6)	5 (4, 7)	22 (19, 25)	29 (25, 32)	40 (37, 44)
Use of illicit substances is moral	4 (3, 6)	4 (3, 6)	16 (14, 19)	20 (17, 23)	56 (52, 60)
Ritalin (methylphenidate)
Ritalin is addictive	11 (8, 13)	26 (23, 30)	59 (56, 63)	3 (2, 5)	1 (0, 2)
Ritalin is effective at improving academic performance	7 (6, 10)	25 (21, 28)	57 (54, 61)	7 (5, 9)	4 (2, 5)
Ritalin use is common among [institution] students	4 (2, 5)	14 (11, 17)	57 (54, 61)	19 (16, 22)	6 (5, 9)
Ritalin should be legally available	2 (1, 3)	5 (4, 7)	34 (31, 38)	25 (22, 29)	33 (30, 37)