Why does my teenager seem so tired?

If your teenager is frequently tired, they’re not alone. As many as one in three adolescents say they regularly struggle with fatigue, defined as feeling exhausted after a normal level of activity. But in teenagers, frequent fatigue or tiredness does not just mean having less energy for school, social activities and other commitments. It can come with long-term consequences – from poorer school performance, to obesity, to even a higher likelihood of having a car accident.

For most teenagers, feeling tired can be addressed with lifestyle changes, particularly around sleep habits. Around one in four adolescents sleep less than six hours a night, well below the recommended amount of eight to ten hours. Some teenagers, however, may remain tired even when they get sufficient rest. This could have to do with their nutrition, stress, or a health condition, whether sleep-related or otherwise.

Here are some of the main reasons why a teenager might seem tired – and how you can help them to get the rest that they need to thrive.

Is your teenager sleeping enough?

The scientific consensus is that teenagers need, on average, between eight and ten hours of sleep per night. In fact, research has found that when they are allowed to sleep as much as their bodies need, adolescents sleep for more than nine hours. Few teenagers regularly log this amount. 

Much of this is because a child’s biological sleep rhythms change as they get older. When children are young, their sleep pressure builds up quickly during the day, meaning they are usually ready for an earlier bedtime. But as a child moves into adolescence, this sleep pressure rises more slowly. This means they no longer feel tired earlier in the evening.

At the same time, the biological rhythms that tell our bodies when to go to sleep – and when to wake up – also shift later. This is a natural process that has been found across a number of societies. In fact, over the entire lifespan, the age at which we are most likely to be ‘night owls’ is about 16 years old for girls and 17 for boys.  After this, our rhythms slowly start to shift to being earlier again.

As a result, when they enter adolescence, even a child who once went to bed early and slept easily can begin to have a hard time with this routine. This is not their ‘fault’, but due to their biology.

Making matters more difficult is that many societies are not built for these later sleep rhythms. Schools and workplaces tend to start early in the morning. As a result, teenagers often do not get the amount of sleep they need.

If your teenager seems frequently tired, therefore, the first step is to support them with their sleep. Because we cannot always choose a later start time for the day, this often means changing sleep habits. Strategies that have been found to be helpful include:

• Going to bed at the same time every day. Because this can be difficult for teenagers to do on their own, parents may need to provide a set bedtime. Research has found that adolescents who have a bedtime set by their parents get more sleep than adolescents who don’t.
• Using the bedroom only for sleep. When activities such as doing homework, hanging out with friends, eating or watching television are kept out of the bedroom, it is easier to associate the bedroom with relaxation, which can help with falling and staying asleep.
• Keeping screens (including phones and tablets) out of the bedroom. Many teenagers – like many adults – stay on their devices late at night. They may also check them if they wake up in the middle of the night. This can activate our bodies and brains, making it hard to get restful sleep, or fall back to sleep if we have woken. Parents can help with this by modelling responsible device behavior themselves.
• Re-setting the body clock each day by waking up at the same time each morning and being exposed to light as soon as possible – ideally natural light – such as by opening the curtains or going outside.
• Not ‘catching up’ on sleep on weekends. While tempting, this change in sleep timings can have a knock-on effect into the week. Waking at the same time daily leads to more, better sleep overall.
• Taking ‘sleep-related cues’ out of the bedroom, particularly for teenagers who struggle with falling or staying asleep. As well as screens, objects like sleep-tracking smart devices or even clocks can draw our attention and remind us of how little sleep we are getting. This has been found to potentially make our sleep worse and make us feel less rested, particularly for people who struggle with insomnia.
• Managing stress and overwhelm. Like smaller children or adults, teenagers who feel worried or anxious often struggle more with sleep. It is important to foster open, supportive communication about their worries. If something specific is a trigger, such as tensions within the family or a high-pressure school schedule, it should be addressed. Mindfulness techniques may also help. 
• Getting physical activity during the day. Studies have found that adolescents who get at least 20 minutes of vigorous exercise four or more days a week are more likely to get enough quality sleep than adolescents who do not.
• Avoiding tobacco and alcohol. Both substances have been linked to sleep being more disrupted and to poorer quality sleep.
• Lowering caffeine intake. While research on caffeine’s impact on sleep is mixed, studies have found that adolescents who drink more caffeine are at a greater risk of having sleep problems. 

For most adolescents, these changes to sleep habits will mean they have more energy and are less tired. However, there are other lifestyle factors that can impact energy levels, too.

How diet impacts adolescent sleep

While often overlooked, nutrition is an important factor in how refreshed we feel.

The world’s most common micronutrient deficiency, for example, is iron. Around one-third of the global population has insufficient iron levels. This includes millions of children and teenagers.

Iron allows the body to make healthy red blood cells, which carry oxygen around our body. If an iron deficiency goes unresolved, it can mean that our red blood cells are not made properly. This is called iron-deficiency anaemia. Both iron-deficiency anaemia, as well as having an iron deficiency without yet experiencing anaemia, can make us feel weak and tired. An iron deficiency also may make it more difficult to sleep well. Even for infants, it can cause frequent night wakes and restlessness. It can also make it hard to fall asleep at the start of the night.

Iron deficiency is especially common both in young children and in adolescents. About 8 in 100 adolescent boys have iron-deficiency anaemia, specifically. Because of the loss of blood during menstruation, teenage girls are at an even greater risk: about 15 in 100 girls have iron-deficiency anaemia. An even greater number of teenagers have iron deficiency without anaemia.

In some societies, iron deficiency is even more common. Because our bodies absorb iron best when it comes from animal sources, mainly meat, those who follow vegetarian and vegan diets are at particular risk.

Iron is not the only nutrient we need to feel energetic. Deficiencies in other nutrients, such as fiber, B vitamins, vitamin C, magnesium and zinc, also are associated with higher levels of tiredness in both adults and children. 

If you are concerned that your teenager has a vitamin or nutrient deficiency, it is important to contact your health practitioner. In some cases, they may recommend supplementation. Often, however, the best way to address a deficiency is through nutrition. One small, controlled study found that when children and adolescents who complained of fatigue were put on a diet high in green vegetables, beef, whole milk and full-fat butter, for example, they slept better and felt more refreshed. The researchers concluded that the biggest impact was due to the green vegetables, which were consumed five times per week – possibly because of their high levels of vitamins A and C, which help our bodies to absorb other minerals including iron.

Other dietary habits may impact sleep, too. There is some evidence, for example, that eating breakfast and having meals at regular times may lessen fatigue. It also has been found that consuming more fast food and sugars can worsen sleep quality. It can go the other way, too, leading to a vicious cycle: the more tired we are, the more likely we are to reach for less nutritious or more sugary foods – which may make us more tired.

Mental health and adolescent sleep

The rapid changes they experience in their bodies, brains and lives can put adolescents at risk of poor mental health. When our mental health is not at its best, we often feel more tired.

One study of more than 3,000 adolescent boys and girls, for example, found that the adolescents who showed more signs of depression or anxiety also were more likely to experience fatigue.

But even in the absence of clinical mental health symptoms, feeling stressed or overwhelmed can make us feel more tired. It can also make it more difficult to fall asleep and stay asleep at night.

There are also strong links between our mental health and insomnia, a sleep disorder that makes it difficult to fall or to stay asleep. Around one in every three adolescents report experiencing insomnia symptoms in the last couple of weeks, while one in 20 meet the clinical criteria for chronic insomnia.

If you think your teenager may be struggling with a mental health issue or with insomnia, it is important to talk about it and get them the support they need. (Here are some tips for how to talk to your teenager about their mental health). For insomnia, this might be cognitive behavioral therapy or mindfulness techniques, which can help to shift our beliefs around sleep and make it easier to relax.

Other health conditions that can impact sleep

For some adolescents (as for some adults), however, making lifestyle changes to sleep and nutrition, and addressing any mental health challenges, may not improve their tiredness. One reason may be that they have a health condition that impacts their ability to get high-quality sleep. This could be a sleep disorder or something else.

Sleep disorders are relatively rare, but still affect millions of adolescents worldwide. The most common is delayed sleep phase syndrome (DSPS), a mismatch between the biological body clock and the environment that can make it hard to fall and to stay asleep. It has been found to affect up to seven in 100 adolescents. Other conditions that can affect how refreshed we feel during the day, even if we were in bed for sufficient time, include sleep-disordered breathing (also known as obstructive sleep apnea), narcolepsy and restless leg syndrome.

Another condition that can make adolescents feel very tired for a long period of time is chronic fatigue syndrome (CFS). This type of fatigue is severe enough that it impacts day to day life, lasts for six months or longer and includes other symptoms, such as headaches, malaise or joint pain. It is relatively rare, affecting only up to 2 per cent of teenagers who report feeling frequently fatigued.

Viral infections also can cause fatigue, even after recovery. With post-viral fatigue, for example, the body still feels tired even after it has cleared a viral infection. While it is often spoken about today in the context of Covid-19, where it is often called “long Covid”, post-viral fatigue can occur after any virus, such as influenza. Exactly what causes fatigue after an infection is still being studied. For the majority of adolescents, it goes away on its own. However, if post-viral fatigue lingers for more than a few weeks after an illness, it is important to consult with a physician.

Other infections can cause tiredness too. Lyme disease, for example, is the most common tick-borne disease in Europe, affecting thousands of children and teenagers. Because ticks are so small and a tick bite does not always leave a rash, it can be easy to miss. But one symptom is tiredness and fatigue.

Other health conditions also can cause low energy, brain fog, fatigue and malaise. This means that if you have worked with your teenager to adjust their sleep habits, nutrition, and mental health, and they continue to feel like they are not getting sufficient rest, it is important to consult with a clinician.