Study suggests 'summer babies' suffer more negative outcomes as adults

Bad news for ‘summer babies’: Children who are the youngest in their class are more likely to get lower grades and suffer depression and drug addiction in adulthood, study warns

  • Experts find a link between being young in a school class and negative outcomes
  • They want more flexibility for kids in relation to when exactly they start school
  • Children may be almost a whole year younger than other children in their class

Children born in the summer who are the youngest in their class are more likely to develop depression and substance misuse disorder as adults, a study reveals.

The London authors claim so-called ‘summer babies’ are also more likely to have low educational achievement, such as poorer grades, by the time they leave school. 

This is not just because they’re missing out on extra learning time, but because there’s something about being less mature behaviourally, cognitive and socially that ‘places a child at risk for many later outcomes’. 

For example, being young in a school class could make kids less accepted by their peers, leading to mental health issues later. 

Summer-born children can be almost 12 months younger than some of their fellow classmates, and have therefore had less time to develop. 

Based on the findings, the team is calling for greater flexibility about school starting age, so that summer born children don’t miss out on nearly a whole calendar year of extra learning. 

Summer-born children are more at risk of depression and substance misuse later in life, the study reveals (stock image)


Attention deficit hyperactivity disorder (ADHD) is a behavioural condition defined by inattentiveness, hyperactivity and impulsiveness.

It affects around five per cent of children in the US. Some 3.6 per cent of boys and 0.85 per cent of girls suffer in the UK. 

Symptoms typically appear at an early age and become more noticeable as a child grows. These can also include:

  • Constant fidgeting 
  • Poor concentration
  • Excessive movement or talking
  • Acting without thinking
  • Little or no sense of danger 
  • Careless mistakes
  • Forgetfulness 
  • Difficulty organising tasks
  • Inability to listen or carry out instructions

Currently, the UK school year runs from September 1 to August 31, so children born towards the end of this period are at an unfortunate disadvantage. 

Being young in a school class – known as having a ‘young relative age’ – also increases the risk of being diagnosed with attention deficit hyperactivity disorder (ADHD), the experts warn.  

The new research has been conducted at the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, in collaboration with the Karolinska Institute and Orebro University. 

‘In the early stages of childhood, this is a significant difference in terms of maturity, behaviour and cognitive abilities,’ said study author Professor Jonna Kuntsi.

‘Behavioural characteristics that are normal in younger children are in some cases being compared to much older individuals, and we can see from the data that there are very real and long-term consequences to being the youngest in a class year.

‘We show that simply a child’s month of birth can place them at a disadvantage. 

‘This is of course a problem, because children’s future outcomes should be fully independent of their relative age at the start of school.’ 

For their study, the researchers wanted to look at the combined effects of young relative age and ADHD on several negative long-term outcomes.  

The study looked at data from 300,000 Swedish individuals from the Swedish National Registers, all born between 1990 and 1997. 

As the Swedish cut-off date for school entrance is January 1, those with a ‘young relative age’ – being young in a school class – are born nearer the end of the calendar year. 

In the study, those with a young relative age were born in November and December, and those with an old relative age were born between January and February. 

All individuals were followed from their 15th birthday to their birthday in 2013, and were between 16 to 23 years of age by the end of follow-up. 

Researchers looked at whether or not they’d had a criminal conviction and took data from the National Patient Register for the occurrence of substance misuse and depression. 

In the individuals without ADHD, young relative age was associated with a 14 per cent increased risk of depression, as well as a 14 per cent increased risk of substance misuse, and a 17 per cent increased risk of low educational achievement.

However, there was no increased risk of criminality detected for this group. 

In the individuals with ADHD, meanwhile, young relative age was associated with a 23 per cent increased risk of substance misuse and 12 per cent increased risk of low educational achievement, but not depression or criminality.   

Being young in a school class (known as having a ‘young relative age’ ) also increases the risk of being diagnosed with attention deficit hyperactivity disorder (ADHD) – a behavioural condition defined by inattentiveness, hyperactivity and impulsiveness (stock image)


Children without ADHD 

– 14% increased risk of substance misuse 

– 17% increased risk of low educational achievement 

– 14% increased risk of depression 

 – No increased risk of criminality  

Children with ADHD

– 23% increased risk of substance misuse

– 12% increased risk of low educational achievement

– No increased risk of depression or criminality   

So although the youngest in a class overall were more likely to experience low educational achievement, substance misuse disorder, and depression in later life, younger children with ADHD appeared less at risk of depression. 

Overall, the prevalence of ADHD was higher in children with young relative age (2.8 per cent of the sample) compared to those with old relative age (1.7 per cent).

Professor Kuntsi said the results don’t necessarily  show having young relative age causes negative outcomes.

‘What our data shows is a longitudinal association – being young-for-class increases the risk for these outcomes later on,’ she told MailOnline. 

The academics note that the negative effects of young relative age is much less common in countries like Denmark, possibly due to the more flexible approach to school starting age there. 

Young children that might not be ready to start school have the opportunity to start school later, and as such are less at risk of experiencing negative side effects seen in other countries. 

It is a practice that the researchers say could be emulated elsewhere, such as in the UK.  

‘Being the youngest child in a classroom can have complex developmental consequences, and can place them at a disadvantage at the earliest stages of their academic life,’ Professor Kuntsi said.

‘If we are to overcome this, there needs to be a greater understanding from decision makers, teachers, and clinicians so that all children have an equal chance to succeed later in life.’

The study has been published today in the Journal of the American Academy of Child and Adolescent Psychiatry. 

Drug addiction, also called substance use disorder, leads to an inability to control the use of a legal or illegal drug or medication (stock image)

Earlier this year, Dr Tammy Campbell, a researcher at the London School of Economics and Political Science, said summer-born primary school kids are disproportionately given the ‘special educational needs or disabilities’ (SEND) label. 

Summer-born children, particularly boys, are much more likely to be given the SEND label by the end of their primary school career, she found.

Nearly half of summer-born boys are categorised as having SEND by primary schools, according to her research paper. 

‘The crux of the problem as I see it is not quite that they have had less time to learn,’ she told MailOnline at the time.

‘It is more that they are simply younger and less developed – and so of course shouldn’t be expected to have learned and developed as much – because they are up to 12 months younger. 

‘Expectations of what is ‘normal’ for very young children should be flexible, and emphasise individual progress and growth rather than static thresholds.’ 

Children with special educational needs and disabilities (SEND) 

SEND stands for special educational needs or disabilities.

Children said to have SEND can receive SEND support in school.  

Children can be recorded with SEND at two levels:

Lower: Decisions about who has SEND are made by the school, and provision is funded by the school. Outside agencies may be involved in assessments and provision in some cases, but not necessarily. Support at this level is not statutory/guaranteed.

Higher: Education and Health Care Plan (EHCP) level: decisions about whether to award an EHCP are made by the local authority (LA). Provision is then statutory and legally guaranteed (in theory), and funded by the LA. This is intended to be for children whose needs cannot be met by existing provision and funding within mainstream schools.

Dr Campbell found that overall patterns are similar for ‘higher’ local authority-funded statutory SEND provision. 

For example, among children reaching Year 6 in 2018, 1.7 per cent of autumn-born girls had been granted statutory SEND provision at some point during primary school, compared 1.9 per cent of summer-born girls, 4.5 per cent of autumn-born boys, and 5.2 per cent of summer-born boys.  

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