Basic symptoms in the general population and in psychotic and non-psychotic psychiatric adolescents

Cognitive-perceptive 'basic symptoms' are used complementary to ultra-high-risk criteria in order to predict onset of psychosis in the pre-psychotic phase. The aim was to investigate the prevalence of a broad selection of 'basic symptoms' in a representative general adolescent population sample (GPS; N=96) and to compare it with adolescents first admitted for early onset psychosis (EOP; N=87) or non-psychotic psychiatric disorders (NP; N=137).

Subjects were assessed with the Bonn Scale for the Assessment of Basic Symptoms (BSABS). Prevalence of at least one 'basic symptom' and mean numbers were compared across the three groups. Logistic regression was used to predict group membership by BSABS subscales; risk ratios were calculated to identify 'basic symptoms' which best discriminated between groups.

The prevalence of at least any one 'basic symptom' was 30.2% in GPS compared to 81% in NP and 96.5% in EOP. Correct classification of EOP when compared to GPS was high (94.0%) and lower when compared to NP (78.6%). Cognitive symptoms discriminated best between EOP and NP.

Alike other prodromal- and psychotic-like experiences, 'basic symptoms' are prevalent in the general adolescent population, yet at a lower rate compared to EOP and NP. The usage of 'at least one basic symptom' as a screening criterion for youth at risk of developing a psychotic disorder is not recommended in the general population or in unselected psychiatrically ill adolescents. However, particularly cognitive 'basic symptoms' may be a valuable criteria to be included in future 'at risk' studies in adolescents.