Mood disorders increased in young adults across the past decade, with smaller and less consistent trends observed in older adults, according to national survey data.

Of more than 500,000 survey participants, the percentage of adolescents ages 12 to 17 (“iGen,” “Generation Z”) experiencing a major depressive episode in the last year increased by 52% from 2005 to 2017, while the percentage of young adults ages 18 to 25 (“Millennials”) experiencing serious psychological distress in the last month was up 71% from 2008 to 2017, reported Jean Twenge, PhD, of San Diego State University, and colleagues.

The same trends were not observed in respondents ages >25, including “Generation X,” and “Boomers,” with a slight decline in psychological distress observed among adults ≥65. The incidence of major depressive episodes was unchanged, or slightly decreased, in respondents ages ≥26, they wrote in the Journal of Abnormal Psychology.

These trends could be explained by the introduction of smartphones in the developmental stages of more recent generations, Twenge, who is also the author of “iGen,” told MedPage Today.

“When you think of how lives have changes from 2010 to 2017, a clear answer is that over time, people started spending more time on phones and on social media, less time face-to-face with their friends, and less time sleeping,” Twenge said. “As we know from other studies, spending more time with screens, less time sleeping, and less time face-to-face with friends is not a good formula for mental health.”

Depression has increased in the U.S. over recent years, with the fastest rise in youth and young adults, according to health insurance data. Certain aspects of digital media, such as the introduction of smartphones and social media, have also been linked to a higher likelihood of major depressive disorder, specifically among Millennials.

Twenge said youth might be more susceptible to some of the effects of digital media because it was such an integral part of their development early on. She also noted that the findings here contrast with other theories that the increase could be attributed to today’s teens being more open about their mental health, or more willing to seek help, she said, as the current study asked about symptoms and behaviors, instead of inpatient or clinical data regarding specific disorders.

“I think it’s possible the change in social lives of young people has been more pronounced in the age of the smartphone,” Twenge said. “Older people may already have an established social network and the change in how they use their social time may not be as extensive as it has been for teens and young adults.”

“Getting your first smartphone at 12 is fundamentally different than getting your first smartphone at 30,” she added.

Twenge and colleagues used responses from the National Survey on Drug Use and Health of individuals ≥12 years. Rates of serious psychological distress were determined through responses to the Kessler-6 Distress Scale, and rates of major depressive episodes and suicide ideation were determined through NCS-Replication interviews. Deaths by suicide were measured through CDC Fatal Injury Reports (1999-2017).

In total, 212,913 adolescents (ages 12-17) responded from 2005 to 2017 and 398,967 adults (≥18) responded from 2008 to 2017. These groups were similar in terms of sex (51% vs 52% female), race, and ethnicity, with over 50% of both samples being non-Hispanic white, close to 15% being non-Hispanic black, and 15% Hispanic in both groups. A slightly higher percentage of the older group had family incomes <$49,999 compared with the adolescent group (55% vs 46%).

Women had greater increases in mood disorders versus men across the number of reported major depressive episodes, suicide-related outcomes, and serious psychological distress, Twenge and colleagues reported.

The percentage of white Americans experiencing major depressive episodes and suicide-related outcomes increased more than it did for other races or ethnicities, although Hispanic respondents had the greatest increase in psychological stress, they added.

Finally, the biggest increases in psychological distress and suicidal ideation were observed in respondents with the highest family incomes, while increases of adult major depressive disorder and suicide attempts were greater in lower income families.

The authors cautioned against overinterpreting the suicide ideation result, as few respondents reported their thoughts about suicide or attempted suicides. However, they noted that since each later generation had increased thoughts of suicide, it appears this increase was due to cohort as well.

Study limitations included its cross-sectional design and the fact that it included only single-item assessments of suicide ideation or attempts. Suicide-related outcomes also weren’t assessed in adolescents, researchers reported, and irritability was not included in the assessment for this group’s major depressive episodes.

The results suggest a need for more research to understand the role of factors such as technology and digital media use and sleep disturbance may play in mood disorder and suicide-related outcomes, and to develop specialized interventions for younger cohorts, the authors concluded. “This work is necessary given the high cost of mood disorders and suicide.”