Some studies have related processing speed with functionality. A more discriminative analysis of different components of this neuropsychological construct is needed.

To measure the performance of a group of patients with schizophrenia in reaction time, processing velocity and sustained attention. To compare the impact on functioning of these three measures.

Ninety-eight outpatients between 18 and 65 years diagnosed with schizophrenia, based on the DSM-V, with a 3-month period of clinical stability, were recruited. Sociodemografic and clinical data were collected: PANSS scale, Akathisia Simpson-Angus Brief Scale, State-Trait Anxiety Inventory (STAI) and Global Functioning Scale (GAF). The following variables were measured: reaction time (SUPERLAB PRO), processing speed (TMT-A, subtest of symbol coding BACS, verbal fluency) and sustained attention (Continuous Performance Test).

Functionality of patients was correlated to Elective Reaction Time (the subject must react to different types of stimuli and to choose between several possible answers) [P=−0.205; P=0.047], but NOT with Simple Reaction Time [P=0.109; P=0.293)]. Functionality was significantly correlated to Symbols Coding (P=0.328; P=0.001), and a trend was observed regarding semantic fluency (P=0.190; P=0.06) and the TMT-A (P=−0.179; P=0.08). In CPT, Correct Detection was correlated with GAF score (P=0.380; P=0.000) but not omission errors. The model of lineal regression shows a differential impact of every measure in global functioning.

Reaction time, processing speed and sustained attention are different variables and each of them have impact on functioning in schizophrenia.