Department of Gynaecology, Obstetrics and Pediatrics Sciences, University of Modena, Modena, Italy
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Abstract |
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Key words: abortion/mood/rhythm/season/suicides
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Introduction |
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Materials and methods |
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In order to define the frequency of the decision to interrupt a pregnancy, the monthly distribution of voluntary abortion was corrected for the estimated number of corresponding pregnancies. For the national data this was achieved by considering voluntary abortion as occurring at the third month of gestation (weeks 812), and by reporting pregnancies terminating with birth to the same period of gestation via the subtraction of 6 months from the month of delivery. The monthly distribution of the ratio of voluntary abortions/total vital pregnancies (pregnancies terminated with voluntary abortion and birth) was then analysed. From the data of our institute, we estimated time of conception, and then calculated the ratio of conceptions terminated with voluntary abortion, on either conceptions of vital pregnancies (pregnancies terminated with abortion and birth) or total conceptions (pregnancies terminated with abortion, birth, miscarriage, and ectopic pregnancy). Data were then compiled at the third month of gestation (weeks 812), by adding 2 months to the month of conception.
Monthly distribution of female and male suicides, as well as monthly distribution of all suicides (males + females) in the years 19951998, were obtained from the national database of ISTAT. In addition the monthly distribution of female suicides in a 4-year period (years 19741977), preceding legalization of voluntary abortion, was also obtained from the same database.
Circa-annual rhythmic distribution in the rates of voluntary abortions and suicides was evaluated by the periodogram method using the RHYTHM programme (Van Cauter, 1979). The periodogram was adapted to analyse the 12 month rhythmicity. As originally described (Van Cauter, 1979
), the method initially tests the significance of the observed time fluctuations against the hypothesis of their purely random occurrence via two different tests. The alternative to being purely random is to test the existence of local correlations, implying that values at given times depend on values at other times, and for the second test, the existence of periodic fluctuations. When the hypothesis of random occurrence of the data is rejected the periodogram method is applied to detect and estimate the possible significant components. A sum of sinusoidal components with a period equal to the integer divisors of the observation span (i.e. 12 months/1; 12 months/2; 12 months/3 etc.) is fitted to the series. A decision procedure devised by Fisher allows the selection of the significant periodicities underlying the process at a given probability of P < 0.05. Up to the first three significant periodical components are included in the theoretical description of the profile. A theoretical pattern is computed according to the minimum of the residual sum of squares. The amplitude of the theoretical pattern is defined as half the difference between maximum and minimum of the theoretical pattern, while the acrophase is the time corresponding to the occurrence of the first global maximum of the theoretical curve. Both the amplitude and the acrophase are furnished with a confidence interval. Periodograms are considered significantly different when described by different periodical components or alternatively when the confidence intervals of either the amplitude or acrophase do not overlap. Accordingly, using the periodogram, analysis estimations of the relative contributions of low and high components in the time dependence of the profile and indications regarding the frequency range and the periodicity or non-periodicity of any components can be obtained. Contingency tables and the
2-test were used to perform the statistical comparison among the rates of voluntary abortions.
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Results |
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Adjunct of clinically evident miscarriages (n = 1004; 8.9% of total conceptions) and ectopic pregnancies (n = 98; 0.8% of total conceptions) did not modify the rhythmic distribution of the decision to abort. Accordingly, the ratio of voluntary abortions/on total conceptions (abortions + miscarriages + ectopic pregnancies + births; n = 11345) showed a sinusoidal rhythm, with a period of 12 months, mesor of 30.3 voluntary abortions/total conceptions, amplitude of 6.9%, and maximum rhythm values in May with confidence limits of ±38 days (Table III).
Periodogram analysis allowed the selection of two 3-month periods, one with a higher (AprilJune) and one with a lower (OctoberDecember) rate of voluntary abortions. The rate of voluntary abortions was significantly higher in the former than in the latter, both in the national (20.3 versus 18.0%, P < 0.0001) and institutional (34.8 versus 30.5%; P = 0.035) evaluations.
The circa-annual rhythm of the decision voluntarily to abort (abortions/abortions + births) derived from the national database and from the medical records of our institute, were in phase with the circa-annual rhythm of the 3481 female suicides (870 suicides/year), observed in the nation between the years 1995 and 1998. The frequency of female suicides showed a sinusoidal rhythm with period of 12 months, mesor of 72.5 suicides, amplitude of 11.1%, and maximum rhythm values in June with confidence limits of ± 37 days (Figure 1
; Table III
). A similar circa-annual rhythm was observed for the 10 456 male suicides occurring in the same time period (
2636 suicides/year)(Figure 1
). The rhythm had a period of 12 months, mesor of 219.7 suicides, amplitude of 9.6% and peak values in June with confidence limits of ±37 days. Similarly, the circa-annual rhythm of male and female suicides together (14 027 suicides) showed a period of 12 months, mesor of 299 suicides, amplitude of 10.1% and maximum peak values in June with confidence limits of ±37 days (Table III
). The circa-annual rhythm of female suicides was also evident in the 2784 suicides (
696 suicides/year) observed in the period preceding the introduction of voluntary abortion in Italy (years 19741977). In this period, the rhythm of suicides showed a rhythm of 12 months, mesor of 58.0 suicides, amplitude of 8.2% and maximum peak values in June with confidence limits ±40 days (Table III
).
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Discussion |
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Suicidal thoughts, consequent to the psychological distress, are frequent among women just prior to voluntary abortion (von der Muhlen, 1978; Rizzardo et al., 1991
), and suicidal attempts or suicidal personalities (Bohme and Marr, 1975
; Campbell et al., 1988
; Lester and Beck, 1988
; Vigeland, 1991
; Gissler et al., 1996
; Currie, 1997
) have been reported to be more common among women deciding to abort voluntarily. Because we could not match voluntary abortions with all the parameters interfering with suicides (age, social and familial status), all female suicides were considered. The almost complete similarity of the seasonal rhythm of female suicides and that of voluntary abortions furnishes valid support for the strong relationship between the two. Voluntary abortion may induce psychological disturbances (Gissler et al., 1996
; Currie, 1997
) and its seasonal rhythm may influence the seasonal rhythm of female suicides. To test this possibility we evaluated the rhythm of suicides by including male suicides and also by evaluating suicides of women in a period preceding the introduction of legalized abortion in our country. On both analyses, the rhythm of suicides remained virtually identical to that observed for female suicides between 19951998. Accordingly, the seasonal rhythm of suicides does not seem to be a consequence of the seasonal rhythm in voluntary abortions. It is more likely that common mechanisms underlie the occurrence of both suicides and voluntary abortions. Circa-annual neurotransmitter modifications within the brain (Sarrias et al., 1989
; Mann et al., 1992
; Maes et al., 1995
; Cleare, 1997
) may render some women more fragile to economic, relational or familial pressures, and it is possible that besides leading to suicide, such concurrent phenomena have an influence on the decision to abort.
Suicides are likely to be reduced by antidepressants (Rihmer et al., 1998) and supportive environments (Phillips and Wills, 1987
; Chew and McCleary, 1994
; Nisbet, 1996
). Indeed, women with previous suicide attempts are less likely to attempt suicide again if they are in a supportive social and friendship environment (Phillips and Wills, 1987
; Chew and McCleary, 1994
; Nisbet, 1996
). Similar considerations may be applicable to voluntary abortion.
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Acknowledgements |
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Notes |
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References |
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Submitted on October 30, 2000; accepted on April 4, 2001.