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Some children are afraid of the dark and prefer to sleep with the bedroom light on. According to a 2018 study, if you still continue to do so in your adult life, you might be exposed to a higher risk of depression.

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In 2006, researchers released a study after testing 324 people. They found that nose pickers had 51% higher chance of carrying the bacteria S. aureus—a bacteria that often resides in the nasal cavity.

▲Were you carrying a backpack that was too heavy when you were a child? That might be the reason why you have back pain today. According to a 2004 study, adults who suffer from chronic back pain already complained about pain or about their backpacks when they were little.

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A study published in the journal Cerebral Cortex revealed that children who watched too much television have lower verbal IQ scores. Another study found that kids who spend too much time in front of the screen could have attention problems in their adolescence.

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The older you get, the more you grow out of the thumb-sucking habit, but it can leave some long-term side effects. This bad habit can affect the alignment of your teeth or even impact the roof of your mouth.

▲This habit can be difficult to break for many children and even adults. Nail biting can damage your teeth, damage the tissue that makes your nails grow, or cause an infection in the skin around your nail.

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Drinking too many fruit juices or other sweet drinks can lead to poor oral health and weight gain.

▲Being too sedentary as a child can affect your adult life. Kids who have healthy activity levels are more likely to have healthy activity levels when they grow up.

▲A child regularly holding their breath when they're frustrated or upset can cause health issues such as blackouts, cardiac arrest, or other long-term health problems.

▲Children who suck on a pacifier for a significant period of time tend to have dental problems. Additional problems with speech or language development may also occur.

▲Some toys can contain lead—which is one of the most common sources of lead poisoning in children—and that can be harmful in the short- and long-term for the child.

▲While not exactly a habit if you're the victim, according to a 2013 research, being bullied in your childhood can take a toll on your mental health as an adult.

▲Too much sun exposure in your childhood can have some heavy consequences and increases the risk of squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), both of which are skin cancers.

▲Parents who don't teach their kids how to cook even basic recipes are not doing them a favor. This will often lead the child to rely on fast food or eating out often in their adult life.

▲A 2011 study published in the Journal of Dental Research states that maternal oral health has an influence on the children's oral health. If a mother has poor oral hygiene, it is more likely that her child(ren) will follow in her footsteps.

▲It is not unusual for children to swallow toothpaste. This can cause short-term stomach pain, but an excessive amount of fluoridated toothpaste can cause serious problems and lower the amount of magnesium and calcium in your body.

▲Overweight children are more likely to become obese adults, according to the Center for Disease Control and Prevention. The risk of developing health conditions like heart disease, high blood pressure, and type 2 diabetes is much higher.

▲A lack of sleep can affect a child's health. A 2016 study showed that it could in fact have a crucial impact on their later life and that they are more likely to suffer from depression and anxiety.

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Children who are exposed to polluted air are at a greater risk of reduced growth, according to the American Lung Association.

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A 2005 study concluded that children who have smoking parents were twice as likely to imitate the bad habit and begin smoking between the ages of 13 and 21.

▲Chewing on your pen caps can be a form of self comfort, but it also results from feeling anxiety or stress. Much like thumb sucking, chewing might also damage the teeth.

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Early childhood adversity and toxic stress can lead to severe health problems like heart disease, cancer, alcoholism, depression, and other chronic diseases.

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Overusing social media can have a detrimental effect on your mental health by making you less confident and causing unhappiness.

▲Parents who have an obsession with regulating food and dissecting eating habits can indirectly influence their children to have a poor relationship with food.

▲Every kid has sniffed markers at least once, but it is actually a pretty serious matter. The dangers of sniffing markers include the possibility of developing heart complications and losing brain cells.

▲A study published in the journal Child Development found that teenagers who tried too hard to act cool in their adolescence were more likely to experience problems with drinking and drugs in their adult life.

▲If you were raised doing chores, you probably thought it was the most annoying thing ever. However, according to Julie Lythcott-Haims, author of the book 'How to Raise an Adult,' children who were raised to do chores are more likely to become independent, empathetic, and collaborative adults.

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Believe it or not, but a lot of what goes on in our childhood influences our adult life and health. Whether it is picking your nose, sleeping with the light on, or biting your nails, the biological side of these harmless acts turns out to have crucial repercussions even years later.

Click through to see which bad childhood habits may affect you today.