More worryingly, experts say, these disorders are undiagnosed and untreated even when the girls attend maternity clinics.
They interviewed close to 200 pregnant adolescents from Kariobangi and Kangemi in Nairobi during their routine antenatal care visits.
Almost 80 per cent of the girls were single, while the rest were either married or living with a partner.
Researchers assessed them for clinical depression, a mental disorder characterised by persistently depressed mood or loss of interest in activities, sometimes leading to suicide.
Half of all the pregnant girls were depressed, according to the PHQ-9 (Patient Health Questionnaire-9) which was used to diagnose and measure the severity of depression.
“We found that 43.1 per cent of the respondents were depressed,” the researchers say in their report, “Prevalence and risk factors associated with depression in pregnant adolescents in Nairobi”, published in the 'Journal of Affective Disorders'.
“The rate of depression among pregnant adolescents may be higher because many are not screened for symptoms of depression or are unaware of perinatal depression,” they added.
The depression was linked to being in school, experiencing intimate partner violence, substance use within the family and having pressure to use substances by family or peers.
The researchers are from the University of Nairobi, Aga Khan University, and from Nairobi Metropolitan Services.
Others were from Unicef, Harvard T. Chan School of Public Health, Washington University at St Louis, New York University, and the Vrije Universiteit of the Netherlands.
Their study, conducted last year, highlights the often-ignored realities that pregnant girls face: depression, substance abuse, and post-traumatic stress disorder.
“Additionally, adolescent pregnancy and motherhood are linked to stigma, discrimination, gender inequities, and the derailment of educational aspirations,” the researchers said.
The majority of the girls were students and the rest were staying at home assisting their parents with family chores. They were aged 14 to 18 years.
A majority indicated that their pregnancy was unplanned. The mean age of sexual debut was 16.2 years and ranged from 13 to 18 years.
The study also sheds light on the lack of contraception for young people.
The Kenya National Council for Population and Development data places teenage pregnancy rate at 18 per cent. This means one in every five girls between the ages of 15 and 19 years, has either had a live birth or is pregnant with her first child.
The rate increases rapidly to 40 per cent among girls aged 19. The situation varies by county with some counties being disproportionately affected.
Centre for Reproductive Rights, a Nairobi-based reproductive health rights lobby, said the needs of this age group are largely ignored.
“For instance, it is okay to support to teenagers who fall pregnant, but not right for them to prevent pregnancy through contraceptives,” said Martin Onyango, associate director of legal strategies for Africa at CRR.
The Ministry of Health says it is illegal to offer family planning methods to children below 18 years.
Last month, Health CS Susan Nakhumicha said this will not change as long as she is health minister, because she is a devout Catholic.
“I am mama kanisa", we have to teach our adolescents to abstain, I believe that with a firm Christian foundation, they will learn to abstain,” she told the media.
Nevertheless, adolescents still access family planning methods, mostly condoms.
At least 49.3 per cent of all sexually active unmarried adolescents use modern contraceptives, according to various studies.
Girls who fall pregnant sometimes opt for unsafe abortions, further complicating their reproductive health outcomes.
The '2013 Incidence and Complications of Unsafe Abortion in Kenya', an MoH study, established that adolescents aged between 12 and 19 years constituted about 34 per cent of patients presenting for post-abortion care in Kenya.
(Edited by V. Graham)
