Mothers-to-be, take note! Smoking during pregnancy may increase the risk of schizophrenia in your baby, a new study has warned.
Researchers from Columbia University (CU) in the US evaluated nearly 1,000 cases of schizophrenia and matched controls among offspring born in Finland from 1983-1998.
Results showed that a higher maternal nicotine level in the mother’s blood was associated with an increased risk of schizophrenia among their offsprings, researchers said.
The study provides the most definitive evidence to datethat smoking during pregnancy is associated withschizophrenia, they said.
Heavy maternal nicotine exposure was associated with a 38 per cent increased odds of schizophrenia, researchers said.
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DISCUSSIONS
In this nationwide population-based nested case-control
study of nearly 1,000 schizophrenia subjects, we demonstrated
an association between maternal nicotine exposure,
quantified as cotinine during gestation, and schizophrenia in
offspring.
For cotinine classified as a continuous variable and
for heavy nicotine use, the association persisted after adjusting
for covariates. There was no clear evidence of mediation of this
relationship by low weight for gestational age, particularly
since it was not a risk factor for schizophrenia in this population.
Moreover, we did not find convincing evidence for
interaction between parental schizophrenia or other psychiatric
disorders and maternal cotinine on a multiplicative or
additive scale. To our knowledge, this is the first biomarkerbased
study to show a relationship between fetal nicotine
exposure and schizophrenia.
The plausibility of these findings is supported by an extensive
literature on prenatal smoking and neurocognition.
Offspring of mothers who smoke have delayed psychomotor
and mental developmental scores; deficits in sustained attention,
verbal learning, and design memory; impaired speech and
language; and lower IQ (2). Low premorbid IQ and other
neurocognitive abilities have been related to schizophrenia (21).
There are several potential mechanisms by which nicotine
alters fetal brain development (3, 6) so as to increase risk
of schizophrenia. Nicotine binds to neuronal nicotinic
acetylcholine receptors, which are essential for proper brain
organization during the prenatal period (6). Prenatal nicotine
treatment decreases the number of cells in whole brain and
particular subregions in the fetal and neonatal periods (22),
consistent with apoptotic processes. The effects of nicotine
induced dysregulation of neurotransmitter systems and
neuromorphology persist beyond the fetal period (6). In
humans, prenatal smoking has been associated with
structural brain changes in adolescence, including cortical
thinning (23) and decreased corpus callosal volume
(4).
These brain anomalies have also been demonstrated
in schizophrenia (24), as have abnormalities of prenatal
brain development (10) and dopaminergic function (25).
Prenatal nicotine is associated with abnormal development
of cerebral inhibitory neurons, a key pathophysiological
defect in schizophrenia ). Neonates of mothers
who smoke during pregnancy
have abnormal inhibitory gating of the P1 auditory evoked response, indicating impaired
cerebral inhibition.
The principal cholinergic receptor involved
is the a7-nicotinic acetylcholine receptor (nAChR) (27).A single
nucleotide polymorphism in CHRNA7, the a7-nAChR gene, is
associated with schizophrenia (28), and the CHRNA7 genotype
has been linked to familial transmission of the P1 sensory gating
deficiency.
Nicotine also causes uteroplacental underperfusion and
increases carboxyhemoglobin levels, with higher fetal than
maternal levels, both of which reduce oxygen availability and
its delivery to fetal tissues, resulting in hypoxia (2). Although
prenatal nicotine exposure is associated with disrupted intrauterine
growth (30, 31) and lower weight for gestational
age (32), in this study there was not strong evidence for a
mediating role of low weight for gestational age.
Conclusions
Prenatal nicotine exposure during gestation was related to an
increased odds of schizophrenia. Given the high frequency of
smoking during pregnancy, these results, if replicated, may
ultimately have important public health implications for decreasing
the incidence of schizophrenia. Further studies are
necessary to address potential residual confounders.More work
is also needed on maternal smoking and other environmental,
genetic, and epigenetic factors. Finally, it will be of interest in
future studies to examine maternal cotinine in relation to bipolar
disorder, autism, and other psychiatric disorders.
Research paper Summary:
Prenatal Nicotine Exposure and Risk of Schizophrenia Among Offspring in a National Birth Cohort
And in other news -
Smoking Weed Can Alter Your Kids’ DNA, Claim Australian Researchers
As increasing numbers of countries and states review and relax their marijuana laws, it seems as though each new day brings yet another study either lauding or demonizing the drug. However, anti-weed researchers will have to really go some way to trump the latest study by a group of scientists from the University of Western Australia, who claim that marijuana use can mutate a person’s DNA, potentially making their children more susceptible to cancer.
The basis for this claim, which is outlined in the journal Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, revolves around a previous study into how certain genetic mutations occur. According to this paper, a process known as chromothripsis – or “chromosomal shattering” – can alter our DNA in such a way that we become more genetically predisposed to develop cancer and other serious illnesses.