The current study sought to examine the

The current study
sought to examine the extent of the association between breastfeeding and
cognitive ability. With acknowledgment of the literature which argues SES to be
a confounding variable in the relationship between breastfeeding and cognitive
ability, SES was controlled for in the present study. Our hypothesis, which
stated that there would be a significant positive association between breastfeeding
and cognitive ability, net of SES, was accepted. Statistical analysis stated
that SES explained 16% of the variance in intelligence. The addition of breastfeeding
revealed an added 2% of the variance, which in turn was statistically
significant.

Although the findings
of the current study remain significant, and are consistent with previous
literature, we are still unable to explore whether the significant results are due
to the biological components of breastmilk and mother-infant bonding. However,
the literature suggests that when stimulation is controlled for, there remains
a significant association between breastfed subjects and their cognitive
ability. Lucas,
Morley, Cole, Lister and Leeson-Payne, (1992) stated
that when either breastmilk or formula was given to new-borns, an effect of the
components present in breastmilk was directly evident. Furthermore, one variable
which was not controlled for in the present study, due to the analysis carried
out with the use of secondary data, is maternal IQ. This potential confounding
variable should not be overlooked and the negative results postulated by Der, Batty and Deary (2006) merit
a discussion. The researchers in question stated that the positive association
present between breastfeeding and cognitive ability was no longer present when
maternal IQ was accounted for. Ronfani et al.
(2015) echoed this finding through data which was collected from 502
mother-child pairs. Yet, so far, only a restricted number of studies have
evaluated this multifaceted relation providing a plausible alteration for
parental factors (Tong, Baghurst, Vimpani, & McMichael, 2007). Perhaps if
maternal IQ was accounted for in the current study, the results may have been
somewhat different.

SES
made the strongest unique contribution to the model. This supports findings
which suggest that SES has a positive relationship with breastfeeding and
cognitive ability (Belfort et al., 2016; Eide et al.,
2016; Khatun et al., 2017). SES has been said to
affect neural development through a range of environmental factors including
parental care, nutrition and drug exposure (Eide et al., 2016). The established
gap in intelligence results in the current study between children from high SES
and children from low SES backgrounds is 6 IQ points. Von Stumm and Plomin
(2015) recognised that this gap doubles by the time children reach adolescence.
Although the literature strongly suggests a positive relationship between
breastfeeding, SES and childhood intelligence, an important question remains; is
there long term of breastfeeding on adult intelligence? This is particularly relevant
with regard to the fluctuation in IQ in the same individuals at different ages
(Ramsden et al., 2011). Victora et al. (2015) concluded that regular
breastfeeding positively correlated with IQ at 30 years of age. This avenue has
not yet been unlimitedly explored and consequently, future research exploring
adulthood intelligence would be recommended.

There were
many limitations to the present study. Firstly, parental recall was the only
form of information used to assess breastfeeding duration. Retrospective studies
are subject to recall bias. Huttly, Barros, Victora, Beria, & Vaughan, (1990) noted
that within a Brazilian sample, mothers of a high SES background were more
likely to overestimate their duration of breastfeeding, while mothers of a low
SES background were not as likely to do so. Similarly Li, Scanlon and Serdula (2005) indicated that
parental recall is accurate for up to three years. Thereafter, the reliability
and validity appears to diminish. Secondly, many participants were lost in the
follow up of this cohort study. A larger sample size would have added more
power to the study. Participants were not given any monetary benefits for participation,
and this in turn may have attracted parents who have particular interest in
their child’s development. Consequently, this sample may not be an accurate
representation of the general population. Finally, while some evidence suggests
that the association between breastfeeding and intelligence depends on the
child’s genotype Caspi et al. (2007), the current sample was
not genetically informative.

The benefits of breastfeeding have been widely advocated;
therefore future research should focus on evaluating the benefits of various
breastfeeding support interventions. Ideally, participants should be randomly
assigned to various intervention groups (similar to the study conducted by Kramer
et al., 2008), which would encourage mothers to breastfeed in addition to the
usual care received in hospitals. The randomisation would then ensure that SES
and maternal IQ would be distributed randomly between the treatment groups and
thus should not confound the treatment effect.

Comprehensively, the present study provided further insight
into the association between breastfeeding duration and cognitive ability. The hypothesis
which stated that there would be a positive association between breastfeeding
and higher scores on cognitive tests, net of SES, was accepted. Questions surrounding
the contribution of biological, genetic and maternal IQ to this association are
potential confounds which were not explored in the current study. Future research
implications include testing cognitive ability in adulthood, accounting for
genetics and maternal IQ, and employing randomised control trials to reliably
test the association between breastfeeding duration and cognitive ability.