Defense mechanisms have been a source of both fascination and frustration for most personality researchers because they are conceptually intriguing but their assessment is often problematic. To aid personality researchers in integrating defense mechanism theory into personality research, we review and critique the major existing self-report defense mechanism measures:

The creation of an observational Constructive Anger Behavior-Verbal Style Scale (CAB-V) and its relation to resting blood pressure (BP) in an age- and sex-stratified, population-based sample is examined. Participants (N = 1,862) provided hypertension risk factor information, had resting BP assessed multiple times, and completed a videotaped interview, which was later coded for CAB-V and Hostile Style. High CAB-V scores remained a significant predictor of lower resting BP when controlling for the effects of standard hypertension risk factors (age, sex, body mass index, physical activity, alcohol use, smoking status, parental myocardial infarction history, education, and diabetic status) and psychosocial measures (anxiety, depression, hostility, social support, and Hostile Style). This relation also remained when excluding known hypertensive persons. Results suggest that constructive anger expression may have an independent beneficial association with resting BP.

We examined whether borderline personality disorder (BPD) and antisocial personality disorder (APD) could be differentiated based on defense mechanisms as measured by observer (Defense-Q; MacGregor, Olson, Presniak, & Davidson, 2008) and self-report (Defense Style Questionnaire; Andrews, Singh, & Bond, 1993) measures. We conducted 2 studies whereby nonclinical participants were divided into borderline and antisocial groups based on scores from the Personality Assessment Inventory (Morey, 1991). Multivariate analysis of variance results revealed significant overall group differences in defense use. Univariate analyses further showed group differences on several individual defenses (e.g., acting out, denial, and turning against self). Together, the findings suggest that in BPD, the defenses may emphasize interpersonal dependency and a tendency to direct aggression toward the self; whereas in APD, the defenses may emphasize egocentricity, interpersonal exploitation, and a tendency to direct aggression toward others. Overall, this study demonstrates important differences in defense use between borderline and antisocial personality groups across both observer and self-report measures.

We hypothesized that increasing anger verbal behavior in an assertive, constructively motivated style should decrease resting blood pressure (BP) and that this behavior may be one mechanism through which hostility relates to BP. We tested this hypothesis by conducting secondary analyses on a single-blind, matched, randomized controlled study of hostility modification and BP. A total of 22 high-hostile male patients with coronary heart disease were matched on age and hostility level and were randomly assigned to either an 8-week cognitive-behavioral hostility treatment (n = 10) or an information-control group (n = 12). Patients were reassessed after treatment and at 2-month follow-up on hostility, observed anger expression, and resting BP. We found that decreases in hostility predicted increases in constructive anger behavior-verbal component, which in turn predicted decreases in resting BP at follow-up. Thus, one of the mechanisms underlying the hostility-BP association may be the lack of constructive anger expression.

Despite the important insights the concept of defense mechanisms may offer to our understanding of human behavior, no standardized definitions of defense mechanisms have been universally accepted. Inconsistencies in the definition and conceptualization of defense mechanisms has limited the practical utility of research involving these constructs. In addition, lack of interrater reliability, use of anecdotal evidence, and reliance on self-reports has retarded their investigation. Conducting methodologically rigorous investigations with a psychometrically sound instrument is the first step in addressing some of the issues concerning defense mechanisms and their theoretical postulates. This study was conducted to determine the reliability associated with the Defense-Q, an observer-based Q-sort measure of defense mechanisms. Thirty participants who had undergone an interpersonally stressful interview (the Type A Structured Interview; Rosenman, 1978) were rated by 11 trained coders, both for their use of the 25 defense mechanisms and for their ego strength. Reliability was assessed using Cronbach's alpha. Individual defense mechanisms demonstrated reliability ranging from .28 (undoing) to .92 (humor), with an average reliability of .73. Coder reliability ranged from .63 to .76, with an average of .69. These results indicate that defense mechanisms can be reliably assessed by the Defense-Q. Reliability of the Defense-Q is compared to existing observational measures of defense mechanisms.