Nearly 20% of Russian teenagers are in the throes of depression.
Alcohol and drug addiction are both symptoms and causes of mental disorder among teenagers, Unicef said.
Child psychologist Anna Kholmogorova from the Moscow State University of Psychology and Education told RIA Novosti that between 10 and 15 percent of Russian school students have severe depression that requires medical help.
The Unicef report said drug usage among the underage was slowly decreasing but this was offset by children taking up alcohol earlier. The number of officially registered alcoholics under 14 rose by 60 percent in 2000-2009.
Teenaged suicides in Russia also exceeded the global average of 10 cases per 100,000 people aged 15 to 19, the report said.
Between 30 and 31 Russians per 100,000 in this age bracket were committing suicides every year in the 2000s, the report said.
Russia was hit by a string of teenaged suicides in the last two weeks, with seven children aged between 12 and 15 taking their lives in separate incidents across the nation.
Experts said the teenagers could have been following each others' lead, thanks to the media coverage each received.