Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. It typically begins in childhood and can persist into adulthood. Some research suggests that motor and vocal tics, which are rapid, repetitive movements or vocalizations, may be more prevalent among individuals with ADHD compared to the general population. This article will examine the evidence on whether tics are a symptom of ADHD.
What are tics?
Tics are sudden, repetitive movements or vocalizations that can involve simple movements like eye blinking or complex behaviors like jumping or repeating words. Tics are classified into two main categories:
These involve involuntary body movements such as:
- Eye blinking
- Shoulder shrugging
- Facial grimacing
- Head jerking
- Arm thrusting
Vocal or phonic tics
These involve involuntary sounds such as:
- Throat clearing
- Repeating words or phrases
Tics can range from mild to severe. In some cases, they can significantly interfere with daily activities. Tics are often preceded by an urge or sensation that creates discomfort, which is temporarily relieved after the tic occurs.
What is the relationship between tics and ADHD?
Research suggests there may be an association between tics and ADHD, meaning the two conditions co-occur at higher than expected rates. Here is a summary of some key research findings:
- Multiple studies have found higher rates of tics, both motor and vocal, in children with ADHD compared to children without ADHD.
- Between 4-26% of children with ADHD may have a tic disorder like Tourette syndrome, compared to around 1% in the general pediatric population.
- The presence of tics is associated with greater severity of ADHD symptoms like hyperactivity, impulsivity, and inattention.
- ADHD and tic disorders appear to share some similarities in their brain anatomy and neurotransmitter activity, like dopamine system dysregulation.
- ADHD and tic disorders seem to run in families, suggesting potential shared genetic factors.
However, while ADHD and tics co-occur more often than expected by chance, most children with ADHD do not have tics. So tics are not considered a core diagnostic symptom of ADHD.
Why might tics be associated with ADHD?
Researchers have proposed several explanations for why tics may be more common in ADHD:
Shared brain mechanisms
ADHD and tic disorders involve some similar abnormalities in certain brain regions and neurotransmitter activity, like dopamine. This shared neurobiology may predispose to both ADHD and tics.
There are likely shared genetic risk factors that can lead to increased vulnerability for both ADHD and tic disorders. Specific genes like SLITRK1 have been linked to both conditions.
Stimulant medications used to treat ADHD like methylphenidate may potentially induce or exacerbate tics in some children. But many studies find stimulants do not worsen tics overall.
Stress and anxiety
ADHD and tic disorders can both be worsened by high stress and anxiety. This may partly explain their co-occurrence.
Some behaviors like squirming and finger tapping may reflect either ADHD hyperactivity or motor tics. Misdiagnosis between the two conditions is possible.
Monitoring tic symptoms
Careful monitoring for tics is important when assessing and treating ADHD given their higher prevalence in this population. Tics may suggest the need for evaluation for a comorbid tic disorder.
Can stimulant medication cause tics?
Stimulants like methylphenidate (Ritalin) and amphetamines (Adderall) are commonly prescribed to treat ADHD. But there has been longstanding concern that these medications may induce the onset or worsening of tics. Here is an overview of the evidence:
- Multiple clinical trials find no increased risk of new tics developing in children with ADHD starting stimulants.
- A few individual case reports have documented new tic onset with stimulant use.
- Some studies suggest stimulants may worsen tic severity in a subset of children who already have a pre-existing tic disorder.
- Tics associated with stimulants often improve when the medication is discontinued.
- Careful monitoring of tics is recommended when starting ADHD children with tics on stimulants.
Overall, there is little evidence stimulant medications directly cause tics. However, stimulants may potentially exacerbate tics in some children with a predisposition for tic disorders. Thorough evaluation and monitoring is important if tics develop or worsen with stimulant treatment.
Tics, ADHD, and Tourette syndrome
Tourette syndrome is a condition characterized by multiple motor and vocal tics. Given tics occur more frequently in ADHD, it’s not surprising that many individuals have both Tourette syndrome and ADHD:
- Around 50-90% of people with Tourette syndrome also have ADHD symptoms.
- Up to 44% of children diagnosed with Tourette syndrome meet criteria for comorbid ADHD.
- People with both Tourette syndrome and ADHD tend to have greater tic severity and more comorbid conditions like OCD.
- Treatments need to target both ADHD and tic symptoms in this population.
The strong overlap between Tourette syndrome and ADHD provides further evidence of a connection between tics and ADHD. However, Tourette syndrome is still considered a distinct disorder from ADHD.
Treating ADHD with co-occurring tics
When ADHD occurs alongside chronic motor or vocal tics, treatment needs to address both conditions. Recommended management may include:
- Stimulant medications for ADHD symptoms, with careful monitoring for tic worsening
- Adding an alpha-2 agonist medication like guanfacine if tics are exacerbated by stimulants
- Behavioral interventions such as CBIT (Comprehensive Behavioral Intervention for Tics) for tic management
- Working closely with parents, teachers, and the child to optimize school functioning
- Cognitive behavioral therapy (CBT) for any co-occurring anxiety aggravating tics
- Referral to a neurologist or psychiatrist if tic symptoms do not improve
No single medication or therapy works for all children with ADHD and tics. An individualized, multidisciplinary approach combining pharmacotherapy, behavioral interventions, school supports, and cognitive-behavioral therapy provides the most comprehensive treatment.
The bottom line
In summary, key points on tics and ADHD include:
- Motor and vocal tics occur more frequently in children with ADHD compared to the general population.
- Exact rates vary, but studies estimate 4-26% of children with ADHD may have a comorbid chronic tic disorder.
- Shared brain mechanisms and genetic factors likely contribute to the overlap between ADHD and tics.
- Stimulant medications do not directly cause tics but may worsen tics in some children with pre-existing tic disorders.
- Careful monitoring for tics is important when assessing and treating ADHD.
- Combined treatment approaches are often needed for ADHD with co-occurring tics.
While tics are not considered a core symptom of ADHD, their higher prevalence has implications for properly recognizing ADHD, optimizing treatment, and managing any tic disorders that emerge. Careful evaluation and monitoring of both ADHD symptoms and tics is essential for the best patient outcomes.