Bruxism in children and adolescents with attention deficit hyperactivity disorder due to medication regimen: prevalence, correlates, and consequences a cross-sectional study

Abstract

Purpose:

Individuals with Attention Deficit Hyperactivity Disorder (ADHD) exhibit more parafunctional habits such as bruxism. Common medications for ADHD include methylphenidate and atomoxetine. This study aimed to investigate the effects of these medications and the severity of ADHD on bruxism.

Materials and methods:

A total of 181 individuals aged 5–18 years with ADHD were divided into three groups: methylphenidate, atomoxetine, and drug-naïve. The Bruxism Checklist and the Conners’ Questionnaire (for assessing ADHD severity) were completed for each participant. The chi-square test was used to compare the severity of bruxism with both ADHD severity and medication type. A one-way analysis of variance (ANOVA) was conducted to compare bruxism and ADHD scores among the medication groups. Data were analyzed using SPSS version 21.

Results:

Bruxism scores were higher in males, whereas ADHD scores did not differ significantly between males and females. Participants treated with methylphenidate had the highest mean bruxism scores. As ADHD severity increased, bruxism scores also increased. A statistically significant difference was found in mean ADHD scores across bruxism severity levels (P = 0.004). ADHD scores were significantly lower in the nonbruxism group compared to both the mild bruxism and the moderate-to-severe bruxism groups (p less than 0.05).

Conclusion:

The severity of bruxism in children with ADHD appears to be related to the severity of ADHD rather than the type of medication. Bruxism is more common in males. Management of bruxism in children with ADHD should adopt a multidisciplinary approach integrating pharmacological, behavioral, and dental strategies

Introduction

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by three main features: inattention, hyperactivity, and impulsivity (1). As one of the most commonly diagnosed psychiatric conditions in children and adolescents, ADHD is associated with mild impairments in brain regions such as the prefrontal cortex (responsible for executive functions like attention and impulse control), the basal ganglia (involved in motor activity and habit formation), and the cerebellum (which plays a role in coordination and timing) (2). Treatment for ADHD typically involves FDA-approved medications, with stimulants like methylphenidate and amphetamine being the first-line options. Other treatments include atomoxetine and alpha-2 agonists, such as guanfacine and (3).

People with ADHD have more oral parafunctions than those without the disorder. One of them is bruxism (4). According to the American Academy of Orofacial Pain, bruxism is defined as a repetitive neuromuscular activity involving the jaw muscles, characterized by grinding, clenching, or locking of the teeth (5). The prevalence of bruxism in patients with ADHD has been estimated to be 57.6% (4). Souto-Souza et al. (6) further highlighted that individuals with ADHD are at an increased risk of experiencing bruxism both during sleep and while awake.

To date, the exact pathophysiology of bruxism remains unclear, though several factors are thought to contribute, including stress, certain medications, systemic conditions, respiratory disorders, and smoking. One proposed mechanism involves a deficiency in dopaminergic and noradrenergic neurotransmitters, particularly within the mesocortical pathway (7). Two commonly used medications in the treatment of ADHD (methylphenidate and atomoxetine) may exert their effects on the severity of bruxism by inducing changes in central neurotransmitter systems (8). Methylphenidate, a stimulant medication, is known to increase muscle activity, which may contribute to hyperactivity in certain muscle groups (9). A group of case-control studies have reported that methylphenidate may induce or exacerbate bruxism in the short term (10, 11, 12). However, other reports suggest that methylphenidate might actually reduce bruxism symptoms (13). Ertugrul et al. (14) found no significant difference in the occurrence of bruxism between patients taking methylphenidate and those who were not. As for atomoxetine, another medication used to treat ADHD, there is limited evidence suggesting it may exacerbate bruxism (15, 16).

Given the conflicting evidence, small sample sizes in existing studies, and insufficient data, we aimed to investigate and compare the effects of these two medications, methylphenidate and atomoxetine, on the severity of bruxism. Furthermore, this study is the first to explore the potential relationship between the severity of bruxism and the severity of ADHD symptoms. The main null hypothesis stated that there would be no difference among study groups in terms of bruxism severity.

Materials and methods

Ethical approval

All procedures have met the ethical standards of human experimentations (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2020. The study protocol was approved by the ethics committee of the Tabriz University of Medical Sciences (IR.TUMS.DENTISTRY. REC.1402.052).

Study design and protocol

This was a cross-sectional, descriptive, and observational study. This study was conducted in accordance with the Strengthening The Reporting of Observational Studies in Epidemiology (STROBE) guidelines (17)

Study population and sample size estimation

The population of the study were children and adolescents aged 5-18 years with attention deficit hyperactivity disorder treated with methylphenidate and atomoxetine who were referred to child and adolescent psychiatry clinics of Tabriz University of Medical Sciences in 2023.

Based on the results of the study by Kammer et al. (4) the prevalence of bruxism in children and adolescents with ADHD is 57.6%. Considering a 57.6% prevalence of bruxism, an estimation error of d = 0.2p, and a 5% type I error, the sample size was calculated to be 181 participants.

Sampling was conducted using a convenience sampling method from specialized child and adolescent psychiatry clinics at Tabriz University of Medical Sciences. Given that studies have shown that age and gender do not significantly affect the prevalence of bruxism in individuals under 18 years of age, the groups were not matched for age and gender (18, 19). Children and adolescents aged 5-18 years with ADHD diagnosis by a child and adolescent psychiatrist based on DSM-V-TR criteria and a minimum medication duration of three months were included in this study (20, 21, 22). Exclusion criteria were the presence of pinworm or parasitic infections confirmed by Stool Exam and Scotch Test, history of receiving other medications related to bruxism, comorbidity with other major psychiatric disorders (intellectual disability, autism, etc.) , IQ below 70 based on the RAVEN test (6, 18, 19, 23, 24).

K-SADS interview

K-SADS (Kiddie Schedule for Affective Disorders and Schizophrenia) is a semi-structured interview aimed at early diagnosis of emotional disorders and psychiatric disorders in school-aged children 6 to 18 years old, based on DSM criteria. (22, 25). In this study, it was used to exclude mood, anxiety, psychotic, trauma and stress-related, obsessive- compulsive, eating and substance disorders.

RAVEN test

The RAVEN test was administered to participants, and those scoring below 70 were excluded. The RAVEN test is a highly valid and reliable non-verbal test designed to measure abstract reasoning and fluid intelligence, with strong construct and predictive validity, as well as high internal consistency and test-retest reliability (26). Furthermore, based on the medication history, participants were divided into three group including, patients receiving methylphenidate (dose 0.5-1.5 mg/kg) , patients receiving atomoxetine (dose 0.5-1.4 mg/kg) and drug-naive patients (27).

Bruxism checklist

After obtaining informed consent from parents/guardians, a skilled examiner (N.Y) completed the bruxism checklist under direct light using a mirror and probe. The examiner was blinded to the patient’s psychological and treatment conditions. The bruxism checklist contains 15 items (28). Which are (1) Presence of wear facets of the teeth, (2) Recent history (last six months) of noises associated with nocturnal teeth grinding as reported by a friend, relative, and/or spouse, (3) Anamnestic report of catching himself/herself clenching the teeth during the day, (4) Anamnestic information of feeling tension and stiffness during the day, (5) Anamnestic account of feeling tension and stiffness upon awakening, (6) Anamnestic report of awakening frequently at night grinding or clenching, (7) Hypertrophy of the masseter and/or temporalis muscle, (8) Feeling of fatigue on the masseter muscles on awakening, (9) Feeling of fatigue on the masseter muscles during the day, (10) Report of awakening at night or in the morning with the jaws locked, (11) Cervical pain on awakening, (12) Awakening in the morning with pain in the masseter and/or in the temporalis muscles, (13) Feeling of body fatigue and/or feeling of having slept poorly when awakening in the morning, (14) Toothache or feeling of discomfort of the teeth on awakening, and (15) Recent history of chronic dislocation of permanent or temporary restorations.

Patients scoring 3-5 points were classified as mild bruxism, 6-10 points as moderate bruxism, and 11 or more points as severe bruxism (28). Also, the Cronbach’s alpha for this checklist was 0.87, indicating good internal consistency. Additionally, ADHD symptom severity was determined using the Conner’s Parent Rating Scale (29). The Cronbach’s alpha value was 0.84.

Statistical analysis

SPSS version 21 (Statistical Package for Social Sciences, IBM, Armonk, NY, USA) was used for data analysis. The chisquare test was used to compare the severity of bruxism with the severity of ADHD and type of medication. Pearson’s correlation coefficient was used to compare bruxism score with ADHD scores. A one-way analysis of variance was used to compare the bruxism and ADHD scores with the type of medication. The significance level was set at p less than 0.05.

Results

A total of 181 children aged 5 to 18 years, with a mean age of 10, participated in this study. 778 individuals were assessed for enrollment. 47 individuals were excluded for the presence of pinworm or parasitic infections confirmed by Stool Exam and Scotch Test. 252 individuals were excluded due to a history of medication regimen. 238 individuals were excluded for having psychiatric disorders. 251 remaining individuals were screened by RAVEN test and 70 were excluded. No data was missing. Finally, 181 individuals were included. (Figure 1).

Figure 1.

Sample selection flow chart based on the STROBE checklist

Further demographic information is presented in Table 1. A statistically significant difference was observed in mean bruxism scores between genders, with males reporting higher bruxism scores than females (p less than 0.05) (Figure 2).

Table 1.

Frequency distribution of sex, severity of bruxism and ADHD.

Variable		N	Percent
Gender	Female	60	33.1
	Male	121	66.9
Severity of bruxism	Non bruxism	111	61
	Mild	38	20.9
	Moderate	26	14.4
	Severe	6	3.7

Figure 2.

Mean bruxism score among ADHD patients stratified by gender variable.

The methylphenidate treatment group had the highest mean bruxism score but it was not significant (Figure 3). No difference was seen between the frequencies of bruxism severities in treatment types. (Table 2)

Figure 3.

Mean bruxism scores of treatment groups

Table 2.

Frequency of bruxism in three treatment type

Bruxism level	Drug-naive	Methylphenidate	Automoxetin	P-value
Non-Bruxism	65.3	55.2	81.1
Mild	23.2	24.1	10.8	0.070
Moderate	10	20.7	5.4
Severe	1.5	0.0	2.7

A significant correlation was observed between increased bruxism scores and increased ADHD scores and its components which the hyperactivity component had the highest correlation with severity of bruxism (Table 3). Also, no statistically significant difference between treatment groups in terms of mean bruxism scores, ADHD scores, and its components was present (p higher than 0.05). (Table 4). Regarding gender, no significant difference was found in mean age, total ADHD score, and its components between males and females (Table 5).

Table 3.

Correlation coefficients of bruxism scores with ADHD scores.

Variables	Pearson correlation coefficient	P-value
Total ADHD	0.212	0.006
Oppositional impulsivity	0.224	0.004
Hyperactivity	0.272	0.001
Cognition problem inattention	0.187	0.016

Table 4.

Mean bruxism scores, ADHD scores, and its components.

Variable		Mean bruxism scores		P-value
	Drug-naive	Methylphenidate	Automoxetine
Bruxism	2.3	2.6	1.9	0.164
Oppositional impulsivity	10.02	10.3	10.05	0.197
Hyperactivity	8.5	9.25	7.2	0.070
Cognition problem inattention	10.74	10.5	10.37	0.640
ADHD (total)	13.1	14.27	12.1	0.103

Table 5.

Frequency distribution of age and mean score of bruxism and scores of ADHD.

Gender
Variable	Male	Female	P-value
Age	10	10	0.961
Bruxism	2.5	1.7	0.37
Oppositional impulsivity	9.98	9.67	0.624
Hyperactivity	8.5	8.3	0.848
Cognition problem inattention	10.3	10	0.842

Discussion

The mean score of bruxism in medication recipient and medication naive patients were 2.32 and 2.29 respectively. No statistically significant difference between treatment groups in terms of mean bruxism scores was seen (p=0.887). A statistically significant difference was observed in mean ADHD scores among bruxism severity groups (p<0.05) (Table 6). According to the results, the moderate to severe bruxers showed the highest levels of ADHD scores and patients without bruxism showed the lowest levels of ADHD scores. Bruxism is a frequently reported issue among children with ADHD, and its severity can be influenced by certain medications, which may either alleviate or worsen the condition (6). There have been documented cases where both atomoxetine and methylphenidate exacerbated bruxism (21, 30). However, no study to date has directly compared the extent of these medications’ effects on bruxism severity or explored the potential link between bruxism severity and the severity of ADHD symptoms. This study aims to address these gaps by investigating these relationships.

Table 6.

Variance analysis comparing the mean score of ADHD according to severity of bruxism.

Variable		Severety of Bruxism		P-value
	Moderate to severe	mild	Non Bruxism
Total ADHD	15.3	14.8	12.37	0.004
Oppositional impulsivity	11.9	10.6	9.2	0.004
Hyperactivity	11	9.8	7.5	0.001
Cognition problem inattention	12.7	10.6	9.6	0.011

The results of the present study indicate that the mean bruxism severity does not significantly differ among groups receiving atomoxetine, methylphenidate, and the control group. However, a correlation was observed between bruxism severity and ADHD severity, and the mean ADHD score significantly differs when comparing the non-bruxism group with either the mild or moderate to severe bruxism groups.

It has been hypothesized that neurotransmitters such as dopamine, serotonin, norepinephrine, and histamine may play a role in the development of bruxism (31). Atomoxetine, a selective norepinephrine reuptake inhibitor, could potentially influence bruxism through its mechanism of action (32). Additionally, one of its side effects is increased anxiety, which could also impact bruxism severity. Multiple studies have reported a connection between anxiety and bruxism (16, 33).

A case study reported that in an ADHD patient with a history of bruxism, atomoxetine use increased bruxism severity. After discontinuing the medication, bruxism severity returned to baseline.

Due to the patient’s ADHD, medication was resumed, and after 12 weeks of follow-up and atomoxetine use, bruxism severity returned to pre-medication levels (16). In another case study of an ADHD patient, bruxism symptoms emerged within 10 days of starting atomoxetine and intensified with increased dosage while disappearing at lower doses. After one week of returning to a high dose, buspirone was added to the treatment regimen, leading to significant improvement in both bruxism and ADHD severity within 10 days. As buspirone, an effective medication for reducing bruxism, was introduced shortly after bruxism onset, this study may not provide reliable insights into the long-term effects of atomoxetine (15). In the present study, bruxism severity was assessed three months after medication initiation. While these two studies reported short-term bruxism exacerbation, the long-term results align with our current study. Reviewing these studies, our results suggest that atomoxetine’s impact on bruxism severity in ADHD patients may be temporary. A similar pattern was observed with atomoxetine in patients using methylphenidate. Mendhekar et al. (12) reported that ADHD patients developed nocturnal bruxism shortly after starting methylphenidate, which completely resolved after discontinuation. When methylphenidate was reintroduced, and patients were followed for two weeks, bruxism symptoms disappeared entirely.

Maleki et al. (34) suggested that medication use could be linked to a higher incidence of bruxism in ADHD patients, with stimulants showing higher rates compared to other medications. These findings contradict the results of our current study. Due to the small sample size, lack of bruxism severity assessment, absence of clinical examination for bruxism, and the use of medications like clonidine and buspirone in some participants, the study’s results may not be reliable (34). Clonidine may reduce bruxism by calming the sympathetic nervous system, while buspirone can help if anxiety contributes to grinding (11, 35). Clonidine reduces bruxism by activating alpha-2 adrenergic receptors, which decreases norepinephrine release and sympathetic nervous system activity, thereby alleviating stress, anxiety, and muscle tension associated with teeth grinding (36). Buspirone helps reduce bruxism by modulating serotonin (via 5-HT1A receptor partial agonism) and dopamine activity, which can alleviate anxiety and stress, common triggers for teeth grinding (37).

Sivri et al. (10) reported that bruxism began within one day of starting methylphenidate in an ADHD patient and disappeared after 4 days. While case-control studies suggest that methylphenidate may have a short-term impact on bruxism in children with ADHD, a study by Ertugrul et al. (14) found no difference in bruxism rates between patients taking methylphenidate and a non-medicated group over six months. These findings align with the results presented in our study. Moreover, in a study by Chin et al. (13) It was stated that methylphenidate could decrease bruxism in ADHD patients, which is in contrast with our findings. Even though this study used polysomnography, which is highly accurate in the analysis of the sample, it has a small sample size and statistical limitations that make it inconclusive.

Several theories have been proposed to explain how methylphenidate might reduce bruxism. Methylphenidate increases extracellular dopamine levels, and elevated dopamine is one of the factors linked to bruxism (38). Both hyperdopaminergic and hypodopaminergic conditions have been suggested to play a role in the development of bruxism (10). Additionally, methylphenidate has been shown to affect other neurotransmitters, such as norepinephrine, which may also influence bruxism (16). The complex and dynamic interactions between these neurotransmitters highlight the need for further research in this area.

Although numerous studies have reported higher bruxism rates in ADHD patients, with a prevalence of 57.6% , no prior study has investigated the correlation between bruxism severity and ADHD symptom severity (6). In our study, we found a significant correlation between bruxism severity and each of the Conners questionnaire scores, including hyperactivity, impulsivity, cognitive-attention disorders, and overall ADHD severity. As Conners scores increased, so did bruxism severity, regardless of the medication used. This correlation was also observed in the non-medicated control group, suggesting a consistent relationship independent of treatment.

In our study, bruxism rates were higher in males than females, consistent with a study identifying male gender as a risk factor for bruxism (39). Conversely, it has been reported that bruxism incidence, subsequent headaches, and temporomandibular joint pain are more common in women (40). Additionally, women tend to be more sensitive to dopamine released from nerve endings compared to men (41). It appears that different factors may trigger bruxism in each gender. In women, depression-related factors are more involved, while in men, anger-related causes play a larger role (40). A recent study also stated that bruxism in ADHD patients is independent of gender (42). Given the varying potential triggers for bruxism in males and females, further research is needed, with careful control of confounding factors and greater standardization of study conditions.

To the best of our knowledge, this was the first study which has evaluated the impact of two common ADHD medications on the bruxism considering the severity of the ADHD. Also, this study highlighted the effect of the gender on the bruxism. The most relevant clinical significance of this study was related to the minimum medication-therapy duration of three months which revealed that conventional medications may not have significant alleviating effects on the severity of the bruxism. This should be a warning for parents and clinicians to follow oral parafunctions during the medication therapy for decreasing the possibility of harms to the dental and periodontal structures. Additionally, these findings should not be interpreted as questioning the necessity or efficacy of pharmacological treatment but rather as an opportunity to refine individualized treatment plans.

Considering that bruxism is a multifactorial condition influenced by psychological, physiological, and environmental factors; non-pharmacological interventions, including behavioral and dental interventions, stress and lifestyle management, physical therapy and exercises should be considered. Multidisciplinary approach by combining pharmacological treatments with non-pharmacological interventions such as Cognitive-Behavioral Therapy biofeedback, stress management, dental interventions such as the use of night guards or occlusal splints would be a more effective plan in order to minimize the clinical signs and symptoms of the bruxism. Reaching this goal among the ADHD patients need collaborative treatment with team work of psychiatrists, dentists, sleep specialists, and physicians.

One limitation of our study was the lack of comparison between different doses of methylphenidate and atomoxetine. Additionally, assessing tooth attrition proved challenging due to the absence of some deciduous teeth in participants. Due to cross-sectional design of the study and considering factors such as cultural variety and therapeutic preferences, the generalizability was not high, therefore systematic review and meta-analysis in this subject is recommended for achieving more external validity.

Conclusion

It appears that the severity of bruxism in children with ADHD is independent of the type of medication used and may be related to the ADHD severity alone. Additionally, gender affects bruxism incidence, with males seeming to have a higher occurrence. Bruxism management should adopt a multidisciplinary approach integrating pharmacological, behavioral, and dental strategies in order to assess efficacy of combined treatment modalities and identify predictors of treatment response.