Applying an Extended Version of the Theory of PlannedBehavior to Illicit Drug Use Among Students

BRIANM CMILLAN2 AND MARKC ONNERUniversity of Leeds

School of Psydegreechology, University of Leeds,, England, EnglandJournal of Applied Social Psychology, 2003, 33, 8, pp. 1662-1683.

Zohreh fathianCandidate of health education & health promotionMedical university of Esfahan

Introduce drug use among young people has been on the

increase in recent years. Data from various drug use surveys in the United Kingdom have founRecreationald that the use of cannabis and other non-opiates has been rising over the last 30 years.

Although many individuals use illicit drugs and experience few problems, there are potential risks involved. Aside from the issues of legality,the use of any drug can be a risk to health. Cannabis smoke contains 50% to70% more carcinogenic hydrocarbons than does tobacco smoke . LSD use may lead to long-lasting psychopathology in vulnerable individuals as may use of ecstasy,. Repeated use of amphetamines causes tolerance and dependence and may result in a condition known as amphetamine psychosis, which is similar to paranoid schizophrenia).

Thus, recreational drug use is a topic, particularly among young people, that is a matter of interest on health and legal grounds

Introduce The present paper examines the usefulness of the

theory of planned behavior (TPB; Ajzen, 1991; Ajzen & Madden, 1986) in understanding intentions to use and self-reported use of LSD, amphetamine, cannabis, and ecstasy in a sample of students.

The predictive role of three additional variables

(descriptive norms,moral norms, and attitude variability) is also examined, along with several hypothesized interactions.

Theory of Planned Behavior

The TPB, which was developed from the theory of reasoned action (TRA;Ajzen & Fishbein, 1980; Fishbein & Ajzen, 1975), is one of the more widelyused frameworks for understanding and predicting behavior in social and health psychology.

The TPB postulates that behavior can be predicted by intentions to perform that behavior, which in turn can be predicted by the attitude toward performing

that behavior, the subjective norm (which refers to the perceived social pressure to perform or not to perform the behavior),

and finally the degree of perceived behavioral control (PBC; the perceived ease or difficulty in performing a behavior, thought to reflect past experience and anticipated barriers and facilitators)

Behavioral Beliefs

Evaluation of Behavioral Outcomes

Normative Beliefs

Motivation to Comply

Attitude towardBehavior Behavioral Intention

Subjective NormsBehavior

Theory of Reasoned Action r

TRA;Ajzen & Fishbein, 1980; Fishbein & Ajzen, 1975

Theory of planned behaviour (TPB)

Azjen (1991) suggested various factors combine to form an intention to act a

certain way.

Attitudes toward behaviour

Subjectivenorms

Perceived behavioural

control

Intention to behave in a certain way

Behaviour

Hmm….How do I use this with addiction?

the perceived ease or difficulty in performing a behavior,

thought to reflect past experience and anticipated

barriers and facilitators

Feelings about

behavior

Behavioralbeliefs

Normativebeliefs—

Others’expectationsNormative

beliefs—Others’

behavior

Controlbeliefs

Efficacybeliefs

Experientialattitude

Instrumentalattitude

Injunctivenorm

Descriptivenorm

Perceivedcontrol

Self-efficacy

Knowledgeand skills oPerform hebehaviorSalien

ceof the

behavior

Intention to perform the behavior

Environmental constraint

Habit

Behavior

OtherFactor

Feelings about

behavior

Behavioralbeliefs

Normativebeliefs—

Others’expectations

Normativebeliefs—

Others’behavior

Controlbeliefs

Efficacybeliefs

Self-efficacy

Feelings about

behavior

Behavioralbeliefs

Normativebeliefs—

Others’expectationsNormativebeliefs—Others’behavior

Feelings aboutbehavior

Behavioralbeliefs

Normativebeliefs—Others’expectations

INTEGRATED BEHAVIORAL MODEL

there should be no or few environmental constraints that make behavioral performancevery difficult or impossible.

if a person has a strong behavioralintention, she needs knowledge and skill to carry out the

behavior.Instrumental attitude is cognitivelybased, determined by beliefs about outcomes of behavioral performance

influencingperceptions of behavioral outcome likelihood or evaluation of outcomes.

normative beliefs about what others think oneshould do and motivation to comply

what others in one’s social or personal networks are doing

(descriptive norm

one’s perceivedamount of control over behavioral performance, determined by one’s perception ofthe degree to which various environmental factors make it easy versus difficult tocarry out the behavior

self-efficacy is one’s degree of confidence in theability to perform the behavior in the face of various obstacles or challenges. This ismeasured by having respondents rate their behavioral confidence on bipolar “certainI could not–certain I could” scales

Normative Influences in the TPB

Previous research suggests that normative influences play an important role in behaviors such as drug use. For example, Leitner et al. (1993) found that 90% of respondents in their survey saw peer pressure as a cause of drug use.

Despite this, studies employing the TPB generally report that subjective norms (the component of the model held to encapsulate normative influences) were the weakest predictor of intentions (Armitage & Conner, 2001).

Cialdini, Reno, and Kallgren (1990) refer to the normative beliefs

used in the usual applications of the TPB as injunctive social norms as they concern others’ social approval or disapproval, and distinguish them from descriptive social norms (ie., perceptions of what others do) and moral or personal norms (i.e., personal rules of conduct).

Ajzen (1991) suggested that moral norms also might directly influence intentions,and Beck and Ajzen (1991) found that the addition of moral norms significantly increased the amount of variance explained in intentions to perform dishonest behaviors by 3% to 6%.

Several other studies have reported that the inclusion of moral norms adds significantly to the prediction of intentions over and above the other components of the TPB (e.g., Kurland, 1995; Parker, Manstead, & Stradling, 1995; Raats, Shepherd, & Sparks, 1995; Randall & Gibson, 1991 ; for a review, see Manstead, 2000).

Conner and Armitage (1 998) found that in 9 out of 10 studies, moral norm was a significant predictor of intentions of 4% to the prediction of intentions..

Focus of the Present Study

The present study examines the application of the TPB to understanding intentions and actual use of LSD, amphetamine, cannabis, and ecstasy over a 6-month period in a sample of students.

We also examine the predictive power afforded by two additional measures reflecting normative pressures (descriptive and moral norms) and investigate interactions among attitude and PBC, attitude variability and attitude, and PBC and intentions

. The consideration of four different drugs allowed us to assess the generalizability across drugs of the proposed relationships

Method

Participants A total of 494 undergraduate students (222 male, 272

female) aged 17 to 54 years (but mainly in the 19- to 22-year age range) at a university in England took part in the first round of the study (representing 62% of those approached). Of these, 461 provided complete data on all drugs and were used in the analysis. A

total of 146 of these undergraduates (95 female, 51 male) completed the second round of the study 6 months later, 136 of whom provided complete data on all drugs and were used in the analysis.3

Measures were assessed by means of an anonymous questionnaire. Participants were encouraged to complete and return the questionnaire, as it made them eligible for a cash prize.

:Material Intention. Intentions to use were measured with the items, “For each drug

listed below, please indicate how often you intend to use that drug over the next 6-month period (if ever) by ticking the appropriate box.” The choices were rated on an 8-point scale ranging from 1 (never) through 4 (everyfew months) to 8 (every day). Higher scores indicate intention to use a drug more fiequently.4

Arritudes. These were assessed by a pair of semantic differentials (two

items;a = .76 for LSD, a = .72 for amphetamine, a = .81 for cannabis, a = .73 forecstasy). The statement “Using this drug over the next 6 months would be . . .”

was completed with the semantic differential choices of bad-good and unpleasant-pleasant. The items were scored on a 7-point scale ranging from -3 to +3,with higher scores indicating more positive attitude.5

:Material

Injunctive norms. These were measured in relation to best friend, other friends,

family, health experts, partner, and people who use each of the drugs (groups identified in a pilot study). A sample item is “My best friend thinks I should not or should use this drug.” The items were rated on a 7-point scale ranging

from -3 (should not) to +3 (should). Motivation to comply with each of the referent groups was

measured with items for each group and each drug. A sampl item is “With regards to using this drug, I want to do what my best friend thinks I should.” The items were rated on a 7-point scale ranging from 1 (strongly disagree)

to 7 (strongly agree). These items were multiplicatively combined and

averaged (a = .80 for LSD, a = .80 for amphetamine, a = .81 for cannabis, a =

.80 for ecstasy).6

:Material

Perceived behavioral control. A belief-based measure of PBC was employed.Control

beliefs were assessed in relation to expense, having important work to do, being in a bad mood, being in a good mood, “going out,” A sample item is “I am in a

bad mood . . ,,” which was rated on a 7-point scale ranging from 1 (infrequently)to 7 Vrequently). Power item measures were taken for each of the control beliefs.

For example, “Being in a bad mood makes my taking this drug . . .,” which was rated on a 7-point scale ranging from -3 (less likely) to +3 (more likely). These

measures were multiplicatively combined and averaged.

:Material

Descriptive norms. Descriptive norms were assessed in relation to best

friend and partner with a single item: “Please indicate, by ticking the box beside each drug, which drugs your partner uses.” The item was scored either 0 (does not use this drug) or 1 (uses this drug). In relation to other friends, family, and health experts, a different single question was used. This item was “Please indicate, by ticking the appropriate box, how many (if any) of the people in your family use each drug” and was scored on a 6-point scale ranging from 1 (none) to 6 (all) The scores on each item were standardized and then averaged (a = .63 for LSD, a = .66 for amphetamine, a = .73 for cannabis, a= .64 for ecstasy).

:Material

Moral norms. Moral norms were measured using a single item for each

drug. The item “It would be morally wrong for me to use this

drug” was scored on a 7-point scale ranging from -3 (strongly agree) to +3 (strongly disagree). Negative scores indicated moral norms not to use a particular drug.

Attitude variability: Attitude variability was assessed using a single item for each

drug (“My attitude towards using this drug varies from time to time-sometimes my attitude is positive, sometimes negative”). The item was scored on a 7-point scale ranging from 1 (strongly disagree) to 7 (strongly agree), with higher scores indicating higher levels of attitude variability for a particular drug.

:Material

Behavior Behavior was measured in the second

questionnaire distributed 6 months after the first with the questions, “Over the last 6-month period, how often (if ever) have you been using each of the drugs listed below?” The item was scored on an 8-point scale ranging from 1 (never) to 4 (every few months) to 8 (every day). Higher scores indicated more frequent use.

Result:

Result

Descriptive norm was a positive significant predictor ofintention for each drug (p < .OOl). Moral norm was a significant predictor of ecstasy use intentions (p < .05) and a marginally significant predictor of cannabisuse intentions (p < .lo). The significant negative contribution of attitude variabil

Attitudes, injunctive norms, and PBC were each significantly associated with intentions. Attitudes or PBC had the greatest influence on intentions compared to injunctive norms for all drugs. In each case, greater intention to use a drug was associated with holding a more positive attitude, perceiving greater pressure to use the drug, and perceiving factors to facilitate rather than inhibit drug use.

The Attitude Variability x Attitude interaction had a marginally significant negative beta weight in the regression equations for LSD (p < .lo) and a significant negative beta weight for ecstasy (p < .05). The PBC x Attitude interactions were positive and significantfor all drugs (p < .001).8

:Result

Result:

as PBC increased, the predictive power of intentionsincreased. Thus, intentions became more predictive of frequency of drug use when individuals perceived factors to facilitate rather than inhibit performance ofthe behavior.

:Discussion

The present findings suggest that the TPB can be used to predict intentions and use of LSD, amphetamine, cannabis, and ecstasy.

The data provide some additional support for the TPB, adding to a considerable body of literature supporting this model (Ajzen, 1996; Conner & Sparks, 1996; Godin & Kok, 1996).

In addition to providing further support for the TPB, the present findings demonstrate the role of additional normative variables and the importance of considering interactions among variables in the TPB. The findings also suggest that attitude variability can be an important consideration when examining the impact of attitudes on intentions.

:Discussion

Interaction Eflects We investigated three interaction effects in the

TPB: Two involved intentionas the dependent

variable (Attitude Variability x Attitude, and PBC x Attitude),

and one involved behavior as the dependent variable (Intention x PBC).

Such interaction effects are of interest because they might indicate boundary conditions for the relationships between variables in the TPB.

:Discussion Ajzen (1 991) predicted an interaction between

intention and PBC in the TPB such that the relationship between intention and behavior varies as a function of levels of PBC.

It was predicted that as level of PBC increases, the predictive power of intention increases. A few studies have demonstrated such an effect in the context of the TPB (e.g., Terry & O’Leary, 1995; White, Terry, & Hogg,1994).

The present study confirms this effect in four drugs (although it was only marginally significant for amphetamine and ecstasy). However, this is the first study to confirm the effect using a belief-based measure of PBC

:Discussion

Thus, in the present case, it was perceiving there to be more facilitators than inhibitors to taking the drug that was associated with a stronger intention-behavior relationship

Norman and Smith (1 995) and Sparks et al. (1 992) hypothesized that attitude variability moderated the attitude-intention relationship.

The present findings with respect to attitude variability confirm this hypothesis when predicting LSD intentions. At higher levels of attitude variability, attitudes were less predictive of intention. However, attitudes remained significantly related to intention at all levels

of attitude variability

:Discussion

A final interaction that we examined was between PBC and attitude In the present study, we employed a belief-based measure of PBC.

As predicted, consistently across drugs, PBC was more strongly associated with intention when attitudes were more positive. In the case of cannabis and amphetamine, PBC was significantly positively associated with intention at all levels of attitude. However, for LSD and ecstasy, PBC was unrelated to intention when attitudes were negative. Thus, as predicted by Eagly and Chaiken, PBC becomes increasingly less important to

the formation of an intention about a behavior as attitude toward the behavior becomes more negative.`

:Discussion

:Discussion شاد وسالمتباشید