[The effect of Christmas joy on the mood among medical doctors - a randomized, blinded intervention study]

Each December Santa's elves spread Christmas joy (JN). Laughter and humour may influence health and stress level. No other study has investigated the effect of JN on the good spirit (DGH) among healthcare professionals.

We performed a single-centre blinded intervention study with crossover at three hospital departments. JN intervention of three days was randomized. Median ± standard deviation was given. The level of significance was p < 0.05.

During a four-week period, we made 24 observations (response rate 67). The laugh index increased from 0.02 in November to 0.03 in December (without JN) and further to 0.05 with JN. At one department, the rise was significant. At a department without morning coffee, the DGH level raised after JN intervention corresponding to the level at the departments with morning coffee before JN intervention.

Christmas atmosphere tended to increase DGH at the morning conferences. JN tended to have an additive effect. JN exposure may be beneficial.

The study did not receive any funding.

The trial was not registered and was kept secret for the participants in accordance with the tradition of Santa's elves.