For 17-year-old Nnaji, the change happened during the global health crisis. With students being schooled from home in early 2021, she found it difficult to focus on her laptop.
So her mother, Nonyi Mike-Nnaji, hired an art teacher.
"Within three weeks into painting, Christine started talking, regained speech, regained composure, behavioral changes, confidence, self-awareness, and she got self-assurance. Her sense of self was phenomenal. Art really heals. When they say art is life, art is really life," she said.
For the past two years Nnaji and her mother have celebrated by holding events for children living in slums.
As the children watch the teenager paint, facilitators teach parents to identify and manage children on the spectrum.
Temitope Adeleke, who works as a speech therapist in a special needs school, says the cost of therapy is often too high for parents.
"A lot of our parents will complain that to get a special-needs teacher is expensive. It is expensive because the materials that we use too, they are expensive. They are not just cheap things," Adeleke said.
In addition to the high cost of therapy and a lack of awareness around her daughter's condition, Mike-Nnaji also says primary caregivers are not given enough support.
Across Sub-Saharan Africa, according to a study published in the National Library of Medicine, a "scarcity of validated tools" has been a barrier to the research and management of autism.
Autism covers a diverse group of conditions related to the development of the brain. It is often characterized by some degree of difficulty with social interaction, communication and atypical behavior patterns.
According to a 2021 report from the World Health Organization, it's estimated that around 1 in 100 children have autism.
The world marks Autism Awareness Month every April.