Onychophagia is defined as chronic biting of the nail plate, nail folds, nail bed, and/or cuticle.
Behavior Modification Treatment Studies | ||||||
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Study | Design | Materials and Measures | Number of Subjects (M, F) | Subject Demographics, Mean Age, (Age Range) | Results | Conclusions |
Koritzky and Yechiam (2011) [25] | Randomized comparative study on the effectiveness of using nonremovable wristbands (n = 40) vs. mild aversion therapy (applying bitter-tasting polish twice a day) (n = 40) for six weeks. Removal of wristband or discontinuation of polish disqualified participant. | Malone–Massler scale for nail biting severity at start of study, then three weeks, six weeks, and five-month follow-up. | 80 (51, 29) | Adults, 25, (19–41) | The NrR group had a lower drop-out rate (12% vs. 26%; p < 0.06) and was equally effective as aversion therapy when considering all participants (Wilks’s lambda: F2.59 = 110.94; p < 0.0001). Aversion therapy was more effective when considering only non-dropouts (Wilks’s lambda: F2.59 = 3.35; p < 0.042). Lower nail-biting scores were maintained five months post study completion compared to scores at the start of the study (t(42) = 8.05; p < 0.0001). | NrRs can be used as an alternative treatment for patients who have noncompliance with aversion therapy. NrRs may produce lasting change in nail-biting behavior. |
Twohig et al. (2003) [26] | Randomized clinical trial on the effectiveness of HRT (awareness training, competing response training, and social support) (n = 15) vs. placebo control (nail biting discussions) (n = 15) for two hours over three sessions. | Nail length measurements (mm) taken before treatment, after treatment, and at five-month follow-up. | 30 (7, 23) | Adults, 21.5, (18–49) | With HRT there was a 22% increase in nail length, compared to 3% for placebo. Differences in nail length were significantly different in the HRT group (12.1 ± 1.9 mm) with longer nail lengths than the placebo group (8.8 ± 1.6 mm; F = 21.2, df = 1.22; p < 0.01). At the five-month follow-up, the HRT group (11.72 ± 2.5 mm) maintained a 19% increase in nail length from pretreatment measurements compared to 0% in the placebo group (8.5 ± 1.7 mm; F = 7.8, df = 1.17; p < 0.05). | HRT is an effective intervention for treating onychophagia with long lasting changes. |
Azrin, Nunn, and Frantz (1980) [27] | Randomized clinical trial on the effectiveness of HRT (awareness training, competing response training, and social support) (n = 45) vs. negative practice (subjects simulate nail biting and tell themselves how ridiculous the habit appears) (n = 45) for five months after one two-hour training session. | Number of nail biting episodes self-recorded by subjects every day for five months. | 97 (38, 59) | Adults, HRT: 28 (11–56), negative practice: 31 (11–64) | Number of nail biting episodes decreased by 99% (10 to 0.3× per day) in the HRT group compared to a 60% (12 to 4× per day) reduction in the negative practice group (p < 0.001). 40% of HRT and 15% of negative practice participants completely stopped nail biting by the end of the study. | HRT was more effective than the negative practice treatment in reducing frequency of nail biting. |
Silber and Haynes (1992) [28] | Clinical trial comparing mild aversion therapy (applying bitter-tasting polish twice a day) (n = 7) vs. use of competing response (fist clenching) (n = 7) vs. control (nail-biting monitoring and positive encouragement) (n = 7) for three weeks after one week of baseline self-monitoring to increase awareness of nail-biting habit. | Nail length measurements (mm), nail fold erosion scale, Malone–Massler scale for nail biting severity, and self-control questionnaire at start of study and at four weeks. | 21 | Adults, mild aversion: 21, competing: 24, control: 22 | Both aversion therapy and competing response showed improvements in nail length (F1.18 = 26.27; p < 0.01). The competing group had decreased nail fold erosions (U7.7 = 8.50; p < 0.05), decreased severity of nail biting (U7.7 = 4.00; p < 0.01), and increased feeling of control (U7.7 = 4.50; p < 0.01) compared to aversion therapy group. | Aversion therapy and competing response techniques are effective in treating onychophagia. The competing response showed more beneficial effects in treating nail biting compared to aversion therapy. |
Pharmacological Treatment Studies | ||||||
Ghanizadeh et al. (2013) [29] | Double-blind, randomized, placebo-controlled clinical trial investigating use of 800 mg/day NAC (n = 21) vs. placebo (n = 21) for two months. | Nail length measurements (mm) taken before treatment, one month after enrollment, and two months after enrollment. | 42 (14, 28) | Children and adolescents, NAC: 9.28, placebo: 10.76, (6–18) | Patients taking 800 mg/day NAC had significantly increased nail length (5.21 mm) after one month compared to placebo (1.18 mm; p < 0.04). No significant difference was observed after two months. Adverse effects included headache, agitation, social withdrawal, and severe aggression. | NAC decreases nail biting behavior in children and adolescents over the short term. |
Leonard et al. (1991) [30] | Double-blind, cross-over trial comparing clomipramine hydrochloride (mean dose, 120 ± 48 mg/day) vs. desipramine hydrochloride (mean dose, 135 ± 53 mg/day) for 10 weeks (five weeks clomipramine + five weeks desipramine) after two-week single-blind placebo. | Nail Biting Severity Scale, Nail Biting Impairment Scale, and Clinical Progress Scale at baseline and weekly until 12 weeks. | 25 (6, 19) | Adults, 32.7, (21–42) | There was a greater decrease in nail biting with clomipramine treatment than with desipramine as measured on the Nail Biting Severity (F = 3.75, df = 1.12; p < 0.04), the Nail Biting Impairment (F = 5.27, df = 1.12; p < 0.02), and the Clinical Progress (F = 7.65, df = 1.12; p < 0.01) scales. Adverse effects included dry mouth, fatigue, insomnia, constipation, sweating, dizziness, and abnormal liver enzymes. | Clomipramine decreases nail biting more than desipramine as measured on three clinical biting scales. |