Research summary by Andreas Hartmann, Paris, France
Tic fluctuations are well known to patients, parents and clinicians. These fluctuations occur during the day, the week, the month and over the year. Regarding the latter, most patients, parents and clinicians will agree that summertime is usually characterized by an overall reduction in tics, whereas the winter months tend to be more difficult.
Davenport and colleagues, based in Calgary / Canada, speculated precisely that, especially given that winters in Alberta tend to be harsh, with very low temperatures and little sunlight exposure. This was investigated in 370 children diagnosed with chronic tics using a standard scale for rating tics (the YGTSS-R) repeatedly over a 12 month period. When correlating the YGTSS-R scores with a specific month, scores were indeed lowest in August (which is also the summer holiday period) and highest in February, when winter “peaks”. However, in subsequent analyses where other variables (age, gender, ADHD, OCD, major depressive disorder, generalized anxiety disorder and treatment for tics) were co-correlated with the YGTSS-R, this correlation vanished. The strongest predictor of tic severity was depression, and it can thus be speculated that the decrease in tic severity during summer may be mediated by better mood but not directly through the weather/warmer temperatures or leisure time/holidays/sports activities.
Empirically, when tics decrease in the summer months, this is mostly attributed to better rest and less anxiety. When schools reopen, tics tend to increase due to anticipation, stress and/or anxiety, at least for a few weeks. Another period when tics increase is often the end of the school year, maybe due to accumulated fatigue. On a personal basis, I also observe tic increases when summertime changes to wintertime (less sunlight ?) in late October/early November, and around Christmas (excitement around the holidays ?). But then, some patients also tic more during the summer months: boredom, loss of structure and routines, or plain joy and excitement may play a role.
In conclusion, even if major fluctuations in tic severity occur throughout the year, they are not always straightforward to predict on an individual basis, so caution is warranted. Also, the factors which we assume to contribute to tic increases or decreases may actually be quite different from the actual cause. The simple assumption that more rest = less anxiety = less tics is not necessarily this linear. In the same vein, when tics increase, quality of life does not necessarily follows, and even the opposite may be true. A classic example is playing video games which tend to increase tics, yet are mostly categorized as pleasurable. Thus, when advising patients and families, we should be factual and empirical about large scale tic fluctuations but also cautious, especially when it comes to explaining tic variations, and linking tic severity with quality of life.
Summary of:
Davenport I, Lethebe BC, Deans C, Martino D, Pringsheim T. The effect of calendar month on tic severity in children and youth with Tourette syndrome.
BJPsych Open. 2026 Feb 10;12(2):e57. doi: 10.1192/bjo.2025.10964. PMID:
41664468; PMCID: PMC12926886.