Is between diet and depression, but they all used

Is There A Link Between Diet And Depression Among Adolescents? A Literature


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This literature review looks at 10
epidemiologic  studies ,investigating whether there is a link between diet
and depression, among the adolescent population and critically evaluates them.
When researching for papers at first 20 papers were derived from various
scientific databases, for example PubMed and Science Direct. However 10 were
excluded due to them not specifically investigating, diet and depression among
adolescents. All 10 papers explored the relationship between diet and
depression, but they all used various methods to measure diet quality such as
cross sectional study and a longitudinal study. Crucial cofounding variables
were not often  taken into account which decreases the accuracy of the
results. In spite of conflicting reports, there was evidence to show that there
is a link between healthy foods and good mental health. Whereas unhealthy food
caused an increase in experiencing depressive symptoms. 


Diet is the food and beverage that an individual consumes and
mental health is ones emotional, social and psychological wellbeing(Plieger et
al, 2015). Depression is one of the many types of mental health disorders,
depression negatively effects the way one feels, thinks and acts(Plieger et al,
2015). In the United Kingdom(UK), 20% of adolescents may experience depressive
symptoms in a year, and it is increasing at an accelerated rate(World Health
Organisation, 2017). As shown in figure 1 the percentage of teens having a
major depressive episode is  increasing
with age.

Figure 1: This
figure shows that as an adolescent becomes older, the percentage of them having
a major depressive disorder  also increases
(Thapar et al, 2012).

Suicide has been rated as the second highest cause of death among
adolescents due to suffering from depression(Patel et al,2007).Adolescents
usually experience depressive symptoms for a long period, and their risk of a
relapse is immense(Milin et al,2003). 
Numerous studies have concluded that the average length of  a depressive episode ranges from 6-9 months.
The longer the period of an episode, can result in an increase chance of it
happening again(Milin et al,2003).  Nevertheless,
a study that was conducted among adolescents where the episode was short,
concluded that the chance of the episode recurring still existed(Rohde et al,

Research investigating the link between depression and diet has
become popular over the last ten years. However the majority of the studies
have shown the link  between diet and
depression in adults, very little has been conducted in  the adolescent population. These adolescent  studies tend to focus on each  nutrients. Studies have examined the impact of
specific nutrients such as omega 3 fatty acids, vitamin B6  and zinc on depression.It has been suggested
that consuming not enough of these nutrients can lead to depressive symptoms (Fulkerson
et al, 2004).Nevertheless assessing how only a single nutrient may have an
impact one’s mood causes an issue (Gardner et al, 2014). Mood regulation can be
affected by serotonin and dopamine, each of these crave an assortment of
nutrients in order to provide the metabolites that are essential , for the
production of  singular neurotransmitters
that are involved in mood regulation(Gardner et al, 2014). Thus it advantageous
 to investigate how eating a meal and
eating patterns can effect depression (Sathyanarayana et al,2008)

Typically, adolescents consume a diet that is high in fat, sugar
and salt, their intake of fresh fruits and vegetables is also relatively
low(Plieger et al, 2015). Only 22% of adolescents eat accordingly in line with
their daily recommended intake(Hidaka, 2012). It is crucial to look at the
adolescent population as  when looking at
the development of the brain during adolescent years and the rise of depression
during adolescence , the effect of diet on depression may apparently be greater
during  those years than in later stages
of life(Le Port et al,2012).

As a result it is paramount that the relationship between diet and
depression in adolescence is investigated. Looking at the minimal evidence that
is available, findings are inconsistent, few studies have recognised a
dose-response association among diet and depression(Jacka et al,2011). Other
studies have not displayed any association (Sinclair et al, 2016).



8 studies showed a consistent association   that
consuming a healthy Mediterranean style diet, filled with fruits and vegetables
is associated with better mental health(Fulkerson
et al, 2004; Bamber et al, 2007; Jacka et al, 2012; Kohlboeck et al, 2012;
Kuhle et al, 2012; McMartin et al, 2012; Rubio-López et al, 2016; Zahedi et al,
2014). However there were 3 conflicting reports in regards to whether pulses
and grains were part of a healthy or unhealthy diet. Whereas
the same 8 studies showed a consistent association that a  western unhealthy diet which consists of a
diet high in red meat and fatty salty/sugary food, is associated with negative
mental health, and one is more likely to experience depressive symptoms.

As well as looking at a healthy and unhealthy diet link to
depression,  the relationship between
overall diet quality and depression has been investigated. 7 studies  have shown a relationship between a good
quality diet and  experiencing less
depressive symptoms  with a small  effect size
(Fulkerson et al, 2004; Bamber et al, 2007; Jacka et al, 2012; Kohlboeck et al,
2012; Kuhle et al, 2012; McMartin et al, 2012; Rubio-López et al, 2016).However
2 studies  mentioned that there is no

relationship between diet quality as a whole and
experiencing  depressive symptoms. Although
these 2 studies did reference how a large assortment and quality  of diet had a link with a decrease in
emotional/mood issues(Brooks et al, 2002; Tajik
et al, 2012).

5 examined the relationship between confectionery and
depression in a cross- sectional design. Of which 3 concluded a significant
prevalence association(Jacka et al,
2012; Kohlboeck et al, 2012; Kuhle et al, 2012). However  1 longitudinal  study showed how there is no relationship
between confectionery and depression(
McMartin et al, 2012). Another single study found no significant link
between oven baked food and depression, nevertheless the study did have an
association between confectionery and depression, but the sample size was small
(Kohlboeck et al, 2012)

5 studies mentioned that consuming sweets and high in sugar
beverages on a daily basis, can be associated with experiencing depressive
symptoms, however in single study this link was only present in females  not in males(Zahedi
et al, 2014).More over 5 studies showed a link between consuming
breakfast and experiencing less depressive symptoms. However,  there were inconsistencies for lunch and
dinner, three study showed that those who did not have lunch and dinner had a
higher risk of experiencing  depressive
symptoms (McMartin et al, 2012; Rubio-López et
al, 2016; Kohlboeck et al, 2012). However one study found no link
between not having lunch or dinner and experiencing depression(Tajik et al,

4 studies asked
an adolescents parent/guardian to give a report on the adolescents diet(Bamber
et al, 2007; Jacka et al, 2012; Kohlboeck et al, 2012; Zahedi et al, 2014).This
can affect the accuracy of the results due to social desirability as well
as  fact that the parent/guardian will
have an  inadequate amount of knowledge,
of what the subject eats when not at home e.g when there at school and with
friends(Herbet et al,1995).

Design study,

7 studies also
used a cross -sectional study, however a cross -sectional  study is not 
as favourable as opposed to a longitudinal study, due to it not being
over a period of time , this will make it hard 
to determine the  association
between diet and depression(Li et al, 2017). A longitudinal  study however is over a period of time but
this type of study was only used in 3 studies (McMartin et al, 2012;
Rubio-López et al, 2016; Kohlboeck et al, 2012)

Measure of diet

6 studies used food
frequency questionnaires(FFQ) which is a reliable tool,  4 studies used other tools to measure dietary
intake, but they were not validated(Brooks et al, 2002; Jacka et al, 2012;
Kuhle et al, 2012; Zahedi et al, 2014). Studies depend on detailed and precise
reporting from the participant( Streiner
and Norman, 2006).Reporting bias can arise for various reasons  such as recall ability and the fact that some
subjects may lie,  they may report that
they consumed healthy foods and not report unhealthy foods  due to social pressures(Higgs and Thomas,

Cofounding variables

Furthermore,  5 studies
did not include socioeconomic status(SES), financial status, parent/guardian
occupation, and  their level of education
(Brooks et al, 2002; Jacka et al,
2012; Kohlboeck et al, 2012; McMartin et al, 2012; Tajik et al, 2016). For the 5 that did the variables were
not measured or controlled consistently. SES is a crucial variable that must be
included in studies due to it being linked to both  diet and depression(Freeman et al,2016). Likewise
many crucial variables such as food introlerance, allergies and medical
condition which can influence  food
choices were not taken into account by 4 studies(Brooks et al, 2002; Jacka
et al, 2012; Kuhle et al, 2012; McMartin et al, 2012).

Gender differences:

3 studies have mentioned how males tend to be more at risk of
consuming a poor diet opposed to females
(McMartin et al, 2012; Rubio-López et al, 2016; Kohlboeck et al, 2012)The 3 studies have shown a  consistent significant associations between
boys consuming a poor diet quality and experiencing depressive symptoms . However
2 studies  have concluded that females
eat more snacks and unhealthy foods than males. Girls were aware of the fact
that unhealthy foods were not good for them, but they chose to consume them
anyway, when  they were under stress
e.g  when studying for exams,  being bullied and home troubles( Brooks et
al, 2002; Jacka et al, 2012)


Having reviewed 10 epidemiological papers, there was a
consistent trend showing how eating healthy foods can better ones mental health.
Whereas consuming unhealthy foods can increase the chance of experiencing
depressive symptoms. Nevertheless there were conflicting reports as too whether
males tend to be more at risk of consuming a poor diet as opposed to females.

Despite the fact that looking at associations between diet
and depression in the adolescent  population is crucial. There is very minimal
that has been conducted compared to the adult population. This review also
highlights the issue  in not using
validated tools to measure diet intake, as mentioned 4 studies,  used tools that were not validated thus to make
a association  is difficult. More
reliable tools in research need to be used such as a food diary, this will
provide more reliable and accurate results(Brzozowski et al,2017).

In addition, not looking at education level of parents, financial
 status and SES made it difficult to
understand any significant association between diet and depression. For the few
that did variables were not measured or controlled consistently as discussed.
As a result of the absence of the variable, the studies should be looked at
carefully because the relationship observed may be due to SES. More research
needs to be carried out with these crucial variables. There were more cross
sectional studies than longitudinal studies, more research should be carried
out using  longitudinal  studies as they are more favourable  as mentioned. 
They can aid intervention studies trying to find an association among
the adolescent population(Hirota et al,2016).More research also needs to
be conducted in the UK.

There are many other contributing factors that can effect
the diet choices than an adolescent makes, this can be due to accessibility, availability
and  food served in schools/colleges(Hirota
et al, 2016). Parents have a crucial role in shaping a adolescent eating
habits, they can teach and  show them how
eating healthy can benefit ones health, and to make them understand different
types of nutrients(Savage et al,2007). Doing this can aid in the food choices an
adolescent will make in the future and when eating away from home. The fact
that healthy food can also be more expensive than unhealthy food can cause a
dilemma in low-income households(Savage et al,2007). Some  low income families live in food deserts,
where there is  peer pressure to eat
unhealthy foods to “fit in”( Dubowitz et al, 2014).

The price of nutritious foods should be cheaper, more
accessible and  should be available  in larger quantities for people of all
socioeconomic levels, so this enables adolescents from well off families and
those from  low-income households to eat
healthy and have better mental health, in order to reduce experiencing  depressive symptoms.

At present treatment for depression among adolescents is cognitive
behavioural therapy, trying to be more active and antidepressants( Lewinsohn et
al,2016).However there should be alternative  treatments that will  not produce side effects as opposed to
antidepressants. More public health intervention should be made, there should
be leaflets and posters in clinics, health centres and at GP’s practise talk
about the importance of diet and its link to mental health.  Talking in schools and colleges will also be


As discussed above, this review addressed issues
in the methods, cofounding variables and design studies e.t.c. If these
problems are not corrected this will hinder future research. Thus it is crucial
to correct these problems in order to establish a strong link between diet and
depression among adolescents. This will aid 
nutritional interventions which will in turn,  reducing the number of