Introduction Sleep is extremely important for humans, but is of particular value to children (Dahl 2007). The duration of sleep that is recommended for children differs with respect to their age, ranging from twelve to fifteen hours during infancy to nine to ten hours in teenagers (NHS 2017). The importance behind this variation in sleep duration is founded in increased rates of brain development during infancy  (Dahl 2007). While there is a large body of research regarding the need for sleep, its true physiological function is somewhat unknown (Dahl 1996). We do, however, know that it is universal and occurs across all species, highlighting its immense value (Dahl 1996). In recent years, we have slept less than ever before, yet our knowledge on how this will affect us is in its infancy (Cline 2010). This states the importance of this essay. Sleep, or lack of, in childhood has life-long implications, and as such, past and future research in the field is highly important. In this essay, I will evaluate the short and long-term implications of not getting enough sleep from a physiological, psychological and mental health standpoint, to elucidate the importance of sleep and sleep hygiene. This will help me to formulate the argument that children who do not get enough sleep face serious negative consequences in many aspects of their lives. Why do we Sleep?   There are 2 main stages to sleep; rapid eye movement (REM) and non-rapid eye movement (NREM) (Carley and Farabi 2016). REM sleep is known as the deeper sleep when one is dreaming and is associated with consolidating learnt tasks (Smith 2001). NREM is known as the slow wave sleep, which plays a major role in consolidating memories (De Andrés et al. 2011). Sleep also affects us physiologically which I will discuss further in the essay. Psychologists have tried to explain why we sleep. Oswald (1966) proposed a restoration theory, stating that sleep existed in order for the body to restore the chemicals it used during the day (Oswald 1966). REM sleep was for revitalising the brain’s processes through protein synthesis and NREM sleep was to restore the body’s biological processes. Oswald’s argument is strengthened by the fact that we experience the most REM sleep during the first five years of life (Smith 2001). This is also the period where our brain develops the most requiring the most protein synthesis (Dahl 2007). However, the reparation of cell and body tissue happens constantly and is not selectively whilst we’re asleep. Physiological Effect   Obesity & Metabolism – Short Term Sleeping less than the recommended amount has been associated with contributing to childhood obesity in preschool children (Mullins et al. 2017). Ten preschool children were required to follow a strict 5-day sleep schedule prior to the study. They then had one day to collect their baseline sleep and then a day where their sleep was restricted. To restrict their sleep they weren’t allowed to nap and they were found to have slept around 3 hours less than on the baseline day. The findings showed that acute sleep loss caused them to consume 21% more kilocalories than on the day of the baseline and 14% more kilocalories on the day after the sleep restriction. The p value for the results was below 0.05, meaning that if there were no association between sleep restriction and overeating then the results seen would only occur in less than 5% of the studies due to study error (Perneger and Combescure, 2017). This also means that we can reject the null hypothesis, which states that there is no association between sleep disruption and overeating (Perneger and Combescure, 2017). The results are therefore scientifically significant. The study was very thorough in the way that it measured the children’s sleep. If a child deviated >15 minutes away from this strict sleep schedule, their assessment was postponed for 5 days so that their baseline could be achieved again. This ensured that the only sleep variable was the restricted night’s sleep, strengthening the findings of this study. With such a small cohort for the study it is not possible to have the diversity of the global child population. Which affects the application ability of the results. The study should be replicated, as a very small sample size can give false positives (Faber et al. 2014). However, the study is scientifically significantly and therefore can be used to compare with other studies. This study can be explained by looking into the effect that sleep has on the hormones associated with appetite. Short sleep duration is widely associated with low leptin and high ghrelin levels in the blood (Taheri, S. et al. 2004). Leptin is a hormone that is responsible for long-term energy balance and therefore making you feel full (Klok et al. 2007). Contrastingly, ghrelin is responsible for making you want to eat in order to gain energy (Klok et al. 2007).  Having low levels of leptin and high levels of ghrelin will have a combined effect, leading to excess calorie consumption (Taheri, S. et al. 2004). This study shows the short-term implications that not……..