[Schizophrenia, from classification to dimensions: value of longitudinal studies].

: There is no clinical sign, cognitive impairment or physiological abnormality pathognomic for schizophrenia. Aetiological factors and neurophysiological abnormalities appear to be heterogeneous. On the other hand, among the three symptomatic dimensions (negative, positive and disorganized), specific negative symptoms may present as early signs in childhood, may exist as essential signs marking disease onset, may be stable during disease progression, may predict an unfavourable long-term outcome, may have a significant genetic component in affected families, and may, be linked to neurological abnormalities when present. Of these symptoms, anhedonia and motivational disorders are the most stable and have the greatest predictive value. They may reflect a vulnerability common to the schizophrenic spectrum and account for the subsequent development of other symptomatic dimensions; this may be observed even when multiple aetiological factors are involved. In relation to their mechanism of action, the therapeutic effects of neuroleptics are consistent with this hypothesis.