Heterogeneity in schizophrenia: A mixture model analysis based on age-of-onset, gender and diagnosis

Abstract

Les délires chroniques survenant tardivement ont été étudiés essentiellement par des psychiatres européens, et se sont vus classés de façon variable tant dans les nosographies européennes qu’internationales. En Allemagne, Manfred Bleuler a défini la schizophrénie tardive, les psychiatres britanniques parlent de paraphrénie tardive et en France ces tableaux cliniques sont classés dans la catégorie des psychoses hallucinatoires chroniques. Les classifications internationales qui ont à une époque individualisé la schizophrénie tardive l’intègrent actuellement dans le groupe des schizophrénies. Pourtant ces formes à début tardif présentent des particularités que nous avons tenté de définir dans ce travail et qui soulèvent la question de facteurs déclenchants, de l’existence d’une prédictivité, voire même orientent vers des notions de diagnostic précoce.Chronic delusion occurring late in life has essentially been studied by European psychiatrists. « Late-onset schizophrenia » was first described and defined by Manfred Bleuler in 1943, as a form of schizophrenia which occurs after the age of 40. Later, British psychiatrists often used the term « Late-onset paraphrenia » interchangeably with « Late-onset schizophrenia » to designate this disorder. However, late-onset paraphrenia is a British concept which includes all delusional disorders starting after age 60. American psychiatrists had little interest in this patient group, so it is only within the DSM III-R that a separate category was created for patients who developed schizophrenia after age 44. There is now no longer a « late-onset » category for schizophrenia within the DSM IV, nor age criterion for the diagnosis of schizophrenia. In the French nosography, schizophrenia is excluded when a non-affective, non-organic psychosis begins after the age of 40. These chronic delusion syndromes fall into a specific French category : « Psychose Hallucinatoire Chronique» (chronic hallucinatory psychosis).Basing themselves on the analysis of many studies, the authors endeavor to define the characteristics of late-onset schizophrenia. The exact prevalence is not known, but is considered lower than 1 %. There is a preponderance of women over men in this form of disease, that could be explained by the relative excess of dopamine type 2 (D2) receptors in young men (compared with young women), and by a protective role played by estrogens until the menopause, among women predisposed to schizophrenia. Studies of families reveal a lower lifetime risk of schizophrenia in first degree relatives of patients with late-onset schizophrenia, than those with an early onset. Most of these patients have been or are married, and had worked for a long time. Generally at the onset of the illness they are isolated and unemployed. Paranoid and schizoid abnormal premorbid personality traits are frequently noted with the diagnosis of late-onset schizophrenia. An association between late-onset schizophrenia and sensory impairment (visual and auditory) is frequently observed and appear to be in link with auditory and visual hallucinations. The analysis of clinical features reveal that the later the schizophrenia breaks out, the more the patient shows delusion and hallucinatory symptoms, which remain limited to his surroundings, whereas in younger patients, delusion has no limit. Moreover, late-onset schizophrenic patients have a lower prevalence of looseness of associations and negative symptoms than those with an earlier onset. The authors note from the few studies on the treatment, that a number of patients responded well to low dose of antipsychotic agents. The use of « atypical » anti-psychotic drugs is recommended, in order to reduce the adverse effects, notably the extrapyramidal symptoms which are frequent in elderly people.Finally, they conclude that patients with late-onset schizophrenia have symptoms very similar to those of patients with early-onset schizophrenia. But, when taking the different forms of schizophrenia-even the late onset ones-into account, raises the question of the role of trigger factors that could guide research on predictive factors and early diagnosis. This may be one explanation for the survival of the French entity « Psychose Hallucinatoire Chonique ».