Adolescence: changes and characteristics of the period

Adolescence is a transitional stage from childhood to adulthood. The World Health Organization defines it as the period from 10 to 19 years of age. It is a time of intense physical, cognitive, and psychosocial development, when habits and behavior patterns that influence health in adulthood are established. [1]

The scientific literature discusses an expanded understanding of this life phase, extending to 10–24 years of age, as social maturity and neurobiological maturation continue into the early third decade of life. This approach facilitates better planning of education, medical care, and social support for young people. [2]

Adolescents develop identities, learn to make decisions, build relationships outside the family, explore roles and activities, and develop independence and responsibility. These developmental tasks are universal and require a safe environment, clear rules, and supportive adults. [3]

It is during adolescence that many risk and protective factors for chronic non-communicable diseases, mental disorders, and injuries are formed. During this period, successful prevention programs yield the greatest impact. [4]

Health and educational services targeting adolescents should take into account the principles of confidentiality, accessibility and friendly communication, as enshrined in international quality standards. [5]

Table 1. Key developmental tasks in adolescence

Sphere	Main tasks
Biological	Puberty, growth peak, restructuring of hormonal regulation
Cognitive	Shift to abstract thinking, planning and risk assessment
Emotional	Self-regulation, recognition and expression of feelings, stress tolerance
Social	Autonomy, friendship and romantic relationships, civic responsibility
Behavioral	Formation of habits of eating, sleeping, activity, media behavior

Based on synthesis reviews of adolescent health.[6]

Physical and sexual development: what is considered normal

Puberty progresses unevenly and individually: some adolescents experience changes earlier than others, while others experience them later, with significant variability in the norm. It's important to monitor the overall trajectory: the progressive development of secondary sexual characteristics, growth, and changes in body composition. Any concerns require a routine consultation with a physician. [7]

The need for energy and building resources increases due to peak growth rates. In the absence of chronic diseases, nutrition should be nutritious and varied, and regular physical activity should be sufficient to maintain healthy body weight and bone density. [8]

The onset of menstruation in girls marks the transition to cyclical blood loss and an increased need for iron. At the population level, in regions with a high prevalence of anemia, weekly prophylactic iron and folic acid supplementation for menstruating adolescents has been recognized as an effective measure. [9]

Adolescents often experience skin and orthopedic issues related to rapid growth and hormonal changes. Most of these conditions are benign and can be corrected with regimen and topical treatments, but if pain, severe deformities, or progression occur, a specialist examination is necessary. [10]

Regular preventive visits allow for the timely detection of deviations in height and weight, problems with vision, hearing and posture, and also the opportunity to discuss intimate issues confidentially and safely. [11]

Table 2. Landmarks requiring attention and consultation

Sign	When to pay attention
Very early or late onset of signs of puberty	Marked deviation from peers, rapid changes over weeks
A sudden drop or jump in body weight	Changes in the background of decreased endurance, weakness, fainting
Persistent pain in the back, chest, joints	Effect on activity or sleep
Very heavy or very infrequent menstruation	Symptoms of anemia include dizziness and weakness.
Obvious asymmetry of the chest or pronounced deformation of posture	Progression, pain syndrome

Based on clinical guidelines for adolescent health and preventive screening.[12]

Brain, Thinking, and Sleep: Why Routine Matters

The maturation of the frontal lobes of the brain and the connections between them continues into the early 20s. This explains the combination of adult intelligence with still-developing emotional regulation and a tendency toward impulsive decisions under strong emotions. Adolescents objectively need an "external prefrontal cortex"—understandable rules and predictable consequences. [13]

Sleep is a key factor in learning, memory, emotional control, and immunity. Professional associations recommend that adolescents aged 13-18 get 8-10 hours of sleep per night on a regular basis. Sleep deprivation is associated with increased irritability, risk of injury, and poor academic performance. [14]

Evening screens, irregular wake-up times on weekends, and afternoon caffeine are common sleep thieves. Simple interventions such as a fixed bedtime, a "digital sunset" 60 minutes before bed, and morning light exposure improve daytime well-being and behavior within just 2-3 weeks. [15]

Daytime physical activity helps normalize circadian rhythms and improves sleep patterns. Teenagers benefit from regular aerobic and strength training, tailored to their interests and abilities. [16]

If chronic sleep deprivation persists despite regimen measures, a doctor's examination is recommended to rule out sleep disorders, depression, anxiety, iron deficiency, and other conditions. [17]

Table 3. Sleep norms and first steps in 14 days

Age	Recommended sleep duration	What to do this week
13-18 years old	8-10 hours	Record bedtime and wake-up times, remove screens 60 minutes before bedtime, and remove devices from the bedroom

The recommendations are confirmed by consensus of relevant organizations. [18]

Nutrition, Micronutrients, and Growth: Adolescents' Challenges

Peak growth spurts increase the need for protein, calcium, vitamin D, and iron. Adequate intake of these nutrients is critical for bone formation and hematopoiesis, especially during intense exercise and high academic workloads. [19]

To achieve peak bone mass during adolescence, widely cited guidelines recommend approximately 1,300 milligrams of calcium per day, with an emphasis on food sources and fortified foods in those with lactose intolerance. Vitamin D is essential for calcium absorption. [20]

Girls' iron needs increase with the onset of menstruation. In countries and regions where anemia is prevalent in more than 20% of girls, the World Health Organization recommends weekly prophylactic iron and folic acid supplements to reduce iron deficiency and improve academic performance. [21]

A high proportion of ultra-processed foods, sugary drinks, and irregular mealtimes increase the risk of weight gain and micronutrient deficiencies. A practical strategy is to fill your plate with vegetables and legumes, add foods high in calcium and iron, and plan snacks for school in advance. [22]

Dietary supplements are generally not necessary for healthy adolescents with a balanced diet. The decision to use supplements is made individually after assessing the diet, season, physical activity level, and laboratory parameters. [23]

Table 4. Critical Nutrients and Daily Sources

Nutrient	Why is it needed?	Product examples
Calcium	Peak bone mass, teeth, neuromuscular function	Dairy and fortified plant-based drinks, yogurt, cheese, tofu, almonds, greens
Vitamin D	Calcium absorption, immune regulation	Fortified foods, fatty fish, eggs, sunlight with skin protection
Iron	Hematopoiesis, endurance, cognitive functions	Lean red meat, legumes, whole grains, nuts; combine with vitamin C
Protein	Growth, tissue restoration	Legumes, fish, poultry, eggs, dairy products
Fiber	Satiety, microbiota, prevention of deficiencies	Vegetables, fruits, whole grains, nuts and seeds

The data are based on international guidelines on nutrition and micronutrients. [24]

Mental Health: Vulnerabilities and Protections

About 1 in 7 adolescents experiences a mental health disorder. The most common are depression, anxiety, and behavioral problems. Untreated problems undermine academic performance and relationships and increase the risk of injury and substance use. Early intervention reduces the burden of illness. [25]

Suicide remains one of the leading causes of death among young people. Paying attention to statements about a reluctance to live, sudden changes in behavior, self-harm, and risky behavior is an essential part of safety. Any direct statements of intent require immediate assessment. [26]

Risk factors include traumatic events, violence, bullying, chronic stress, sleep disturbances, substance use, and a lack of supportive adults. Protective factors include strong connections with family and school, self-regulation skills, access to helplines, and timely assistance. [27]

An assessment of psychosocial status during an appointment can be conducted using a structured survey based on the HEADSSS scale, which covers home, school and nutrition, leisure, psychoactive substances, sexuality, suicidal thoughts, and safety. This format helps ensure that important topics are not missed. [28]

If signs of depression, anxiety, eating disorders, substance use or self-harm are present, referral to a specialist and a joint plan with the family and school are necessary. [29]

Table 5. Early signs of emotional difficulties

Sign	What to do
Loss of interest in usual activities, isolation	Calm conversation, risk assessment, appointment with a specialist
Problems with sleep and appetite	Establish a routine, discuss stressors, and consult a doctor
Declining academic performance, absenteeism	Contact the school to arrange support.
Self-harm, talk of death	Immediate safety assessment and assistance
Sharp mood swings due to conflicts	Family action plan, psychotherapy if necessary

The criteria are based on international information materials on adolescent health. [30]

Social and digital environment, activity and free time

Adolescents need at least 60 minutes of moderate-to-vigorous physical activity daily, including muscle- and bone-building activities several times a week. This reduces the risk of obesity and depression and improves sleep quality. Limiting prolonged sitting is beneficial for health. [31]

Digital technologies benefit learning and social interaction, but excessive screen time and exposure to violent content are associated with sleep problems, anxiety, and aggressive behavior. Family media plans, shared agreements, and "digital sunsets" reduce conflict and nighttime stimulation. [32]

Safe relationships with peers and in romantic relationships include respect for boundaries, consent, protection from violence, and access to accurate information about sexual and reproductive health. Health services should be teen-friendly and confidential. [33]

Life skills—emotion management, problem solving, and turning down risky opportunities—reduce the likelihood of trauma, substance use, and conflict. These skills are developed through school programs and trainings when coordinated with family support. [34]

A balance of study, activity, and rest protects cognitive function and mental health. A regular schedule, workload planning, and realistic expectations help avoid burnout. [35]

Table 6. Mini-plan for an active and safe week

Direction	At least for a week	Practical steps
Activity	60 minutes a day	Walking sections of routes, sports of interest, strength training 2-3 times
Dream	8-10 hours at night	Rituals, light in the morning, remove screens within 60 minutes
Studies	Plans and pauses	Technique of short cycles with breaks, limit multitasking
Media	Agreed media plan	Public spaces for devices, discussion of content
Social connections	Live communication	Family activities, clubs, and volunteering

The recommendations are consistent with international guidelines on activity and adolescent services.[36]

Prevention, vaccinations and medical observation

Preventive visits during adolescence include assessments of growth and development, vision and hearing, blood pressure, nutrition and sleep, psychosocial screening with confidentiality, and discussions of safety and relationships. Frequency is described in current preventive care plans. [37]

Vaccination schedules are updated according to the national calendar. In most countries, revaccinations against diphtheria, tetanus, and whooping cough, as well as vaccination against human papillomavirus, are relevant during adolescence according to the current schedule. The choice of a specific schedule depends on age and health status. [38]

The World Health Organization has endorsed the possibility of one- or two-dose HPV vaccination regimens for adolescents, which expands access and increases coverage. For immunocompromised individuals, at least two doses are indicated, and three doses if possible. [39]

In countries with a high prevalence of anemia in menstruating adolescents, weekly iron and folic acid supplementation programs are recommended as part of school or community health programs. This reduces iron deficiency and improves learning outcomes. [40]

During the visit, it's important to focus not only on "what not to do" but also on "what to develop": sustainable activity and sleep habits, communication skills, media literacy, and planning the study load. This focus increases the adolescent's engagement and strengthens the alliance. [41]

Table 7. Basic checklist for a preventive visit

Block	What to discuss
Growth and development	Height, weight, body mass index, proportions, secondary sexual characteristics
Lifestyle	Sleep, nutrition, activity, media plan
Psychosocial screening	Home, school, nutrition, leisure, psychoactive substances, sexuality, suicidal thoughts, safety
Vaccinations	Calendar update, human papillomavirus according to the scheme
Plans	Personalized 3-6 month goals and how to track them

The structure meets modern standards of adolescent-oriented assistance. [42]

Red flags and action plan

Statements of intent to harm oneself, actual self-harm, signs of violence, use of dangerous substances, acute psychiatric symptoms, acute chest pain, severe shortness of breath, repeated syncope, sudden neurological symptoms, and unexplained bleeding require immediate evaluation. [43]

Emergency management includes ensuring safety, access to emergency care, informing responsible adults, and coordinating plans with the educational organization. After stabilization, planned follow-up assessment and support are provided. [44]

In cases of persistent decline in academic performance, prolonged isolation, chronic sleep deprivation, and food refusal, early consultation with a specialist is required. Early intervention reduces risks and improves the prognosis. [45]

It's helpful for families to have a written crisis action plan with emergency services and specialist contact information. Having predetermined steps reduces anxiety and speeds up the process of getting help. [46]

Even without emergency risks, regular check-ups and shared goals help keep you on track for healthy habits and academic success. [47]

Table 8. Quick plan in case of a crisis

Step	Action
1	Assess safety, remove dangerous objects, do not leave alone
2	Contact emergency services and inform responsible adults.
3	Provide escort to the medical facility
4	Agree on a return to school plan and support measures
5	Schedule a follow-up visit and follow the recommendations

The recommendations are consistent with international standards for the quality of adolescent care. [48]

A reminder for parents and teachers

Maintain a sleep schedule of 8-10 hours, at least 60 minutes of daily activity, and a consistent media plan with a "digital sunset." These three habits protect behavior, academic performance, and emotional well-being. [49]

Set short, measurable goals with your teenager every 3-6 months: routine, nutrition, studies, sports, relationships. Track small but regular steps and progress, and reward their efforts. [50]

Don't wait for it to "go away on its own" if there are red flags. Early intervention is more effective than late intervention and reduces health and educational risks. [51]