Subthreshold symptoms and vulnerability indicators (e.g., eye tracking dysfunction) in schizophrenia.

Subthreshold symptoms in schizophrenia can be prodromal signs of a psychotic relapse. In people without schizophrenia, similar symptoms may indicate the presence of disorders termed schizophrenia spectrum disorders. Subthreshold schizophrenia-like symptoms may indicate a genetically transmitted higher proneness to schizophrenia. Such a higher liability to develop schizophrenia is ascertained on a symptom level. In genetic studies, asymptomatic members of a pedigree are therefore classified as unaffected although they may possess the genes in question. On a biological level, eye tracking dysfunction has been shown to fulfill certain criteria for a vulnerability indicator and therefore promises to offer more information on genetically transmitted proneness to schizophrenia even in people without psychopathological symptoms. Subthreshold symptoms may warrant treatment. The database for prophylactic treatment in populations at high risk, especially those without symptoms, is currently very small.