1.1. Tourette Syndrome
Once believed to be a rare disease, Tic Disorders [
1]—including Tourette Syndrome—make up 1% of the population, and up to 20% in childhood [
2].
The disorder mainly affects males by a male to female ratio of 3–4:1; TS begins before age 18, usually around age 6 [
3]. In youth, the disorder often increases in severity peaking in the prepubertal period, while in adulthood, in 50–75% of cases, tics improve dramatically [
4,
5,
6,
7].
Recently, TS studies showed high correlations of tics with behavioural disorders such as Attention Deficit Hyperactivity Disorder (ADHD), Obsessive-Compulsive Behaviours/Disorders/Symptoms (OCB/ OCD/OCS), anxiety, depression and poor impulse control e.g., SIB (Self-Injurious Behaviour) and NOSI (Non-Obscene Socially Inappropriate behaviour) [
8].
Anatomically, basal ganglia and substantia nigra are considered the neuroanatomical regions associated with Tourette Syndrome (TS), Parkinson’s Disease (PD) and other movement disorders. Whereas, from an etio-pathological point of view an alteration of dopaminergic synaptogenesis appears to determine TS symptoms [
9].
Many famous artists were affected by TS, such as Samuel Johnson [
10]. Several authors [
11,
12,
13,
14] examined the possible TS diagnosis of Mozart, hypothesising that the syndrome actually contributed to the musician’s creativity. However, it remains unclear if Mozart was truly affected by TS. His behaviour could have been due to a wide spectrum of neurobehavioural disorders. Zanaboni et al. [
15] analysed the creative personality of a sample of 23 Italian TS subjects between 6 and 18 years old and of a healthy control group through Williams’ Creativity test; by results, TS subjects obtained greater creative scores compared with controls in the Flexibility subtest. Wei [
16] studied creativity in a group of 127 Taiwanese TS children and a control group of 138 Taiwanese by parents’ reports. In the Elaboration subtest of Creative Thinking, TS patients were less creative than controls, whereas most TS parents reported their children to have high academic achievement.
Creativity in TS adults has never been studied in literature; for this reason, our group decided to pursue this issue in adulthood.
TS dopaminergic theory is supported by the observation of reduction or suppression of symptoms—and creativity skill, as said above—in a substantial number of patients using dopamine receptor blockers such as haloperidol or pimozide. Also, tetrabenazine, a dopamine-depleting drug that inhibits the vesicular monoamine transporter 2 (VMAT2), is effective for various hyperkinetic movement disorders, including TS [
17,
18]. Results from a study on TS subjects show that after two years of tetrabenazine therapy, 80% of patients have a long-term improvement of symptoms [
19]. However, more recent data are suggesting a still more complex picture, whereby also alterations in the GABAergic system may play an important role in the pathophysiology of TS [
17].
1.2. Parkinson Disease
Parkinson Disease is one of the leading causes of neurological disability for individuals over 60 years of age. PD impacts an estimated 4.5 million people across the world’s 10 most populous countries [
20].
In PD there is a loss of dopaminergic neurons in the pars compacta of the substantia nigra (SNpc) with the presence of “Lewy bodies” due to misfolded aggregated alpha-synuclein protein.
The “cardinal signs” of PD are resting tremor, rigidity, bradykinesia-akinesia, postural instability and one-sidedness of the symptoms [
21]. Patients can show freezing, i.e., the inability to start or carry on a movement [
22]. Moreover, during complex and automated tasks, i.e., writing or a speech, motor control mechanisms can be lacking [
23].
Also in TS subjects, complex and automatic movements can be lacking and can, therefore, generate a variety of tics, such as writing or walking or speaking or reading tics.
PD non-motor symptoms include urinary diseases issues, constipation, skin problems, sleep difficulties, cramps and paresthesia, cognitive decline, depression and other emotional changes. Depression, anxiety and emotional changes may also occur in TS patients. Actually, in a longitudinal study by Lin et al. [
24] stress levels and tic severity were evaluated in a sample of 45 children with TS and/or OCD, and in a sample of 41 healthy control children. In general, psychosocial stress level was higher in patients with TS compared with the control group. Moreover, those who had higher levels of stress were more likely to have a more severe disease course and major complications. The Social Impairment component is therefore essential for TS assessment, considering that exacerbation of tics is often preceded by stressful life events.
PD treatment is principally pharmacological, i.e., dopaminergic therapy. Moreover, PD surgical treatment, i.e., Deep Brain Stimulation (DBS), is reserved for severe and refractory patients [
25,
26].
More recently, Automated Mechanical Peripheral Stimulation (AMPS) is used in PD patients to treat motor deficits. This orthopedic device repetitively and automatically stimulates specific points of the foot to activate brain areas involved in the management of motor functions [
27].
1.3. Creativity
There is a plethora of definitions for creativity [
28]. According to Tudor Powell Jones [
29], creativity is the combination of flexibility, originality and ability to adopt readily new and unusual cognitive patterns in order to solve problems.
Williams’ creativity model, the one used at Milan Tourette Syndrome Centre, defines creativity as the ability to generate ideas or innovative artistic products.
For several years, researchers such as Flaherty [
30] have hypothesised that high dopamine levels in the mesolimbic area improves working memory, facilitating mental connections and original thoughts.
Among the different studies [
31,
32], Limb and Braun [
33] of the Johns Hopkins University School of Medicine in Baltimore decided to monitor the brain activity of six jazz pianists in order to find out the brain areas of creative improvisation. The authors concluded that the ability to improvise (the “peak” of creativity and self-expression) appears to be the result of a reduction of self-control and planning in the brain.
Moreover, in our clinical experience, TS patients have a strong predisposition for the arts (music, painting, expressive writing and theatre) and for jobs requiring creativity and divergent thinking.
The literature reports many cases of people at the onset of their PD who developed increased artistic skills apparently secondary to dopamine drugs [
34]. Furthermore, according to the neurologist Israeli R. Inzelberg [
35], patients with PD assuming dopamine suddenly manifested creative activities. In addition, an Italian research group [
36] hypothesised that dopaminergic therapy could encourage creative thinking in some patients with PD.
Differently, Canesi et al. [
37] evaluated whether artistic production and creative thinking are influenced by dopamine therapy or artistic skills in a sample of (1) professional artist PD patients (2) PD patients with artistic production (3) PD patients without artistic production. These groups were compared with healthy controls. Creativity scores were higher in healthy professional artists and in professional artist PD patients. PD patients without artistic production and healthy control without artistic production showed creative scores without significant difference. Creativity scores were not significantly correlated with dopamine dosage and duration. Authors suggested that further studies in “on” and “off” medication of PD patients are needed to understand these controversial results.
In this sense, fundamental appears to be the type and dose of medication of the patient because, as mentioned above, the intake of dopamine agonists can increase not only the frequency of being engaged in artistic activities, but also it changes the artistic quality of patients’ creative products.
To conclude, creativity manifests itself differently in TS and PD. These diseases affect people of different ages: TS mostly affects children and adolescents [
3], while PD affects adults and the elderly [
20]. Based on the available data, we suppose that individuals with TS have a creative personality predisposition, unlike PD subjects who may be compromised in their creativity because of reduced production of dopamine caused by the disease. Therefore, the aim of the study is to verify the hypothesis of TS group of patients having higher creative scores than PD group of patients.