Psychiatry Research 152 (2007) 273 – 275 www.elsevier.com/locate/psychres
Summer birth and deficit schizophrenia in Tunisia Lassad Kallel a,b,c,⁎, Jerome Brunelin b,c , Ahmed Zghal a , Raja Labbane a , Jean Dalery b,c , Thierry d'Amato b,c , Mohamed Saoud b,c a
Service de psychiatrie «C» Hôpital RAZI, La Manouba, Tunisia EA 3092, Vulnérabilité à la Psychose de la Prédiction à la Prévention, UCBL Lyon1; CH «Le Vinatier», 95 Boulevard Pinel, 69 677 BRON cedex, France c IFR 19, Institut Fédératif des Neurosciences de Lyon (IFNL), Hôpital cardioloque, Bâtiment B13, 59 boulevard Pinel, 69 394 Lyon cedex 03, France Received 9 December 2005; received in revised form 10 February 2006; accepted 5 March 2006
Abstract Summer birth has been associated with the deficit Schizophrenia syndrome, while DSM-IV schizophrenia is associated with winter birth. We confirm these monthly differences in a Tunisian sample of patients with schizophrenia, with a summer birth peak (n = 34 deficit patients) and an expected winter birth peak (n = 46 non-deficit patients). © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Deficit syndrome; Schizophrenia; Season of birth
1. Introduction The deficit schizophrenia syndrome according to the criteria of Carpenter (Carpenter et al., 1988) has been explored by numerous research teams at various levels, i.e. demographic, clinical, neuropsychological, neurological and with neurophysiological techniques. Some authors propose to isolate the deficit schizophrenia syndrome as a specific nosographic entity, distinct from non-deficit schizophrenia regarding psychopathology, etiopathogenesis, physiopathology, and functional prognosis. In order to confirm the existence of a deficit form of schizophrenia distinct from a non-deficit one, some authors have focussed on monthly birth distribution. Through several ⁎ Corresponding author. EA 3092, Service du Pr Dalery, CH «Le Vinatier», 95 Boulevard Pinel, 69 677 BRON cedex, France. Tel.: +33 4 37 91 51 00; fax: +33 4 37 91 51 02. E-mail address: [email protected]
original studies performed in various Western countries (England, Ireland, Scotland, Spain, United States), Kirkpatrick and colleagues reported that June/July births were significantly associated with the deficit schizophrenia syndrome (Messias et al., 2004), while DSM-IV schizophrenia was generally associated with winter birth (Davies et al., 2003). However, some authors failed to identify such monthly variations (Dollfus et al., 1999), justifying further investigation. In the present study, our purpose was to confirm this atypical monthly birth distribution in a Tunisian sample of patients with schizophrenia screened with deficit schizophrenia syndrome criteria. 2. Methods 2.1. Subjects DSM-IV patients with schizophrenia were categorized as deficit subjects (DS, n = 34) and non-deficit
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L. Kallel et al. / Psychiatry Research 152 (2007) 273–275
month the distribution of number of births between DS and NDS, we used a Fisher chi-square test at a significance threshold of 0.05. 3. Results
Fig. 1. Percent of birth by month for patients with deficit and nondeficit syndromes.
subjects (NDS, n = 46) using the Schedule for the Deficit Syndrome (SDS; Kirkpatrick et al., 1989). All the psychometric assessments were carried out by an investigator blind to the month of birth. Results are presented as mean ± standard deviations. The two groups did not differ (results from Student's t-test) for age (31.3 ± 7.6 vs. 34.8 ± 8.4 years), educational level (7.55 ± 5.22 vs. 5.86 ± 5.31 years), illness duration (7.3 ± 5.4 vs. 9.1 ± 5.6 years) and sex ratio (28/6 vs. 33/13 male/female). All patients were born in North Tunisia, from latitude 37–15N to 35.28N and from longitude 10–44E to 08– 43E; mean elevation is about 3 m. Temperature ranges between 25 °C and 35 °C from May to October (75 °F to 90 °F) and 15 to 25 °C for the other months (from 60 to 75 °F). Precipitation is defined any kind of water that falls from the sky as part of the weather. This includes drizzle, rain, hail, sleet, or snow. There is more than 30 mm of water by month (1 in.) from October to April and less than 10 mm by month (0.5 in.) from May to August. Diet is the Mediterranean diet. Psychopathology was assessed by the Positive And Negative Syndrome Scale (PANSS). Compared to NDS, DS had significantly higher PANSS negative subscale scores (27.88 ± 4.34 vs. 24.50 ± 6.47; t-test; P = 0.001), and lower PANSS positive subscale scores (13.64 ± 3.40 vs. 17.30 ± 4.43; t-test; P = 0.0001), without differences for the general psychopathology subscale (44.88 ± 8.32 vs. 43.93 ± 6.16). For dysphoria (depression + hostility + guilt + anxiety), no significant difference was observed between the two groups (8.23 ± 1.76 vs. 8.17 ± 1.98).
We reported significant monthly birth differences between the two groups (Chi2 = 173.2618; df = 11; P b 0.00001). More DS were born in June (12% vs. 2%; Chi2; df = 1; P = 0.03) and July (18% vs. 2%; Chi2; df= 1; P = 0.0006), while more NDS were born in January (11% vs. 26%; Chi2; df = 1; P = 0.02). No difference was observed between the other months (Fig. 1). 4. Discussion We found a significant June and July birth-peak for DS and a significant January birth-peak for NDS. These results paralleled the literature (Messias et al., 2004; Kirkpatrick et al., 2002) and could confirm the relevance of the concept of deficit schizophrenia syndrome in this Tunisian sample of patients with DSM-IV schizophrenia. As expected, the two groups are significantly different for PANSS positive and negative symptoms scores, but neither for general psychopathology scale scores nor for age, educational level or illness duration. Such results support the hypothesis of a different monthly birth distribution in deficit vs. non-deficit schizophrenia, the first one being associated with a summer birth excess while a winter birth excess characterizes the second. This difference could suggest the existence of a specific etiological factor underlying deficit schizophrenia. No specific agent has clearly been identified, but seasonal variations in Borna virus infection (Waltrip et al., 1997), sunlight exposure and vitamin D synthesis (McGrath, 1999) and/or nutritional factors could contribute to the association between month of birth and the symptom profile of individuals with schizophrenia (Torrey et al., 1997). Nevertheless, further studies remain necessary to validate the concept of deficit schizophrenia as a fully or partially distinct entity with a specific etiopathogenesis (Kirkpatrick et al., 2001). References
2.2. Analysis To compare the two groups, we used independent samples Student's t-test at a significance threshold of 0.05 for quantitative variables (age, education level, illness duration, PANSS scores) and chi-square test for qualitative variables (sex ratio). To compare month by
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