The present investigation attempts to describe the correlation between sleep-time masticatory muscle activity (MMA) and psychological symptoms by the use of a four-channel electromyography (EMG) home-recording device in a group of 15 healthy volunteers completing a battery of psychometric questionnaires for the assessment of anxiety, depression and anger. The integrated EMG signal was adopted to quantify the work (μV × s) produced by each of the four muscles (bilateral masseter and temporal) during the 5-h recording span and per each 1-h increment. The duration of MMA events and the muscle work during the first hour of sleep was related to trait anxiety scores for both masseter (P= 0·007) and temporalis muscles (P= 0·022). Trait anxiety was also significantly correlated to the total amount of MMA duration (in seconds) of the temporalis muscles (r= 0·558;P= 0·031). The present investigation provides support to the hypothesis that the duration of sleep-time masticatory muscle activity, especially during the early phases of a night's sleep, may be related to anxiety trait and not to anxiety state, depression or anger. These findings may support the view that features related to the individual management of anxiety, viz. trait, are likely to be more important than acute episodes of anxiety, viz. state, in the aetiology of sleep-time masticatory muscle activity. The role of other psychological symptoms is likely to be less important.