We wanted to explore the validity of measuring the tendency to worry and to overthink, in the Portuguese context. 714 medical students completed the following measures: Worry and Overthinking (two items each) “I worry a lot”, “The people around me consider that I worry a lot”, “I think a lot over things”, “The people around me consider that I think a lot over things”; Eysenck Personality Inventory (EPI) Neuroticism and Extroversion (NE-EPI/E-EPI); Arousal Predisposition Scale (Arousability); Revised NEO Personality Inventory (NEO-PI-R); Neuroticism facets Anxiety, Angry, Depression, Impulsiveness and Vulnerability; Profile of Mood States Positive and Negative Affect (POMS-PA/POMS-NA).

Worry and Overthinking were correlated (p < .001). Temporal stability was high (Worry p < .01; Overthinking p < .01; Worry+Overthinking p < .01). The 4 items factor structure yielded a single factor (a = .836). A factor analysis of these items with EPI items showed that they loaded highly (>.50) on the NE-EPI.

Worry and Overthinking were positively correlated with negative traits: NE-EPI, Arousability, POMS-NA, Neuroticism-NEO-PI-R (all p < .001) and with NEO-PI-R-N facets: all p values < .001, with the exception of Impulsiveness (p < .05). They were negatively correlated with positive traits: E-EPI and POMS-PA (all p < .001).

Based on Worry and Overthinking means and SD and considering frequencies five groups were formed: High worry/overthinking; High worry/low-medium overthinking; Medium worry/overthinking; Low worry/medium-high overthinking; High worry/overthinking. Groups mean comparisons significantly differ in positive and negative traits (means increased/decreased, respectively, from group 1 to 5). We provide preliminary evidence for the usefulness of this measure in this population.