The three notebooks are filled with doodles, comic strips, riddles and little stories, rendered and written in pencil.

One quirky drawing has a parrot mouthing its response to the poser: What do you get when you cross a centipede with a chicken? Answer: Drumsticks for everyone.

The illustrations spring from the fertile imagination of Evan, the eldest of Doreen Kho's four children.

The 43-year-old businesswoman says her son once asked her: "Mom, do you know why I started to draw comics? Because my comics will make people smile and laugh."

Ironically, Evan himself wrestled with depression and was often teary. The condition led the 11-year-old to hurl himself from the 16th floor of a condominium in central Singapore last November.

His heartbroken mother says: "It's difficult to say he's in a better place. Not when he often told me how much he loved me and how his best place was with me, and nowhere else."

After much wrestling, Ms Kho, who has also been diagnosed with depression, decided to go public with her story. "I don't want him to have died in vain. I want to justify his life, it was too short.

"I want people to be aware of depression, which is still a stigma. I want them to know it is nothing to be ashamed of because depression is as much an illness as cancer... I hope by talking about Evan's death, more people can be saved."

Her voice turns soft as she adds: "I've always thought I can do everything but I couldn't save my son."

By any yardstick, Ms Kho is an accomplished woman. Despite family circumstances which forced her to shoulder heavy responsibilities from a young age, she went on to become a successful entrepreneur.

She secured the Singapore franchise for well-known Korean cosmetic and skincare business The Face Shop in the mid 2000s. As its chief executive, she built and expanded it from one to more than 20 stores in under 10 years. She sold the chain, together with two other skincare ventures Belif and VDL, to South Korean conglomerate LG three years ago.

The elder of two daughters of a teacher and his factory supervisor wife, Ms Kho grew up in a household which was far from typical.

Their Ang Mo Kio home was shared with her paternal grandmother, uncle and aunt.

Her uncle suffered from lupus, a chronic auto-immune disease, and did not leave his room during the day for more than 10 years because he thought he was contagious.

Her aunt survived meningitis as a child and became intellectually disabled as a result.

When Ms Kho was 14, her mother died of stomach cancer leaving her husband, a stern and aloof man, withdrawn and depressed. Many a night, Ms Kho would find him sitting in the living room, sobbing quietly with a towel around his head.

Although the former student of Cedar Girls' Secondary and Serangoon Junior College got into the National University of Singapore to read geography and theatre studies, she dropped out after six months. "I wanted to be independent. I did not find purpose in what I was learning," says the articulate woman who cut her professional teeth in an events management company.

Over the next few years, Ms Kho, who married an army regular when she was 22, had stints in different professions including insurance and advertising.

Meanwhile, developments at home tested her resilience and strength of character. Within a short span of time, both her father and grandmother were felled by strokes. To make matters worse, the latter also had dementia.

"It was a trying period. I had to bathe and feed her, change her diapers. But our bond grew."

When she was 26, Ms Kho and her sister, then working as an interior designer, decided that they couldn't hold down a regular job and look after the two elders as well as their aunt at the same time.

They opened an interior design firm so that it would give them the flexibility they needed. The going was tough but they did well enough to soon hire three employees.

After three years, Ms Kho and her sister decided on another venture. They succeeded, after tough negotiations, in securing the Singapore franchise rights for The Face Shop.

Ms Kho says: "All we had was the insurance money left to us by our mother. We had two other partners. Our first shop opened in Bugis in 2005. It was do or die. If it failed, we'd have lost everything."

Fortunately, it took off - and in a big way.

In 2006, 10 years after she got married, Evan came along. By then, Ms Kho's father and grandmother had died. It was a difficult pregnancy and lumbered her with a host of medical problems including a bloated kidney. At 24 weeks, her water bag leaked.

"The doctor told me if I gave birth then, my child would be dead. It was too early," recalls Ms Kho, who was then put under observation. "I remember having meetings in the delivery suite because I had more than 10 outlets by then."

Three weeks later, an extremely premature Evan was born. A normal pregnancy is about 40 weeks.

"I didn't even get to hold him. I heard the doctor say '10 fingers and 10 toes' and they just pushed him into the intensive care unit. His lungs were in danger of collapsing and the doctor warned that he might have problems with his hearing, speech and sight."

Evan was in the ICU for a month, and the high dependency ward for another.

"He was a fighter. When he came home, we were all so happy."

Evan, says his mother, was the "prince" not just of the family but at The Face Shop.

"I'd take him to the office every day," says Ms Kho who went on to have three more children, now aged between six and 10.

When her second child arrived, she set up a crib in the office. "I raised them there. It was a family environment. Everyone was an auntie or a jie jie," she says, using the Mandarin word for sister.

Evan was an affectionate and precocious child. However, he related better to adults than to other children. Although extremely intelligent, he also sometimes appeared to have a delayed reaction to situations and other people.

Still, Ms Kho did not suspect anything was amiss.

The business grew. But juggling work with motherhood was often stressful. An extremely driven person, she also had very high expectations of herself.

"With the staff, I tried to be nurturing. With the children, I tried to be loving. And with business, I tried to be firm," she says, adding that she was diagnosed with depression and prescribed medication which helped to keep it under control.

Her condition, however, took a bad hit when her intellectually disabled aunt drowned in a pool after a suspected heart attack.

"I got her to work in the office so that I could keep an eye on her. When she died, it was very traumatic. Going into the pantry where she always was made me feel so sad," says Ms Kho who often broke down at work and in front of her children.

In 2013, she started negotiations to sell her business. The family also decided to migrate to Australia two years later. Her husband and children moved to Melbourne first while she stayed behind to tie up all loose ends over the sale. She'd fly out to Melbourne every Thursday and return to Singapore on Sunday.

"The constant flying in and out was very traumatic for Evan. We didn't notice he was having behavioural problems," she says.

Ms Kho joined her family in 2015. The move and the change in pace - she found herself with nothing to do except school runs and meal preparations - did not help her depression. In 2016, the family moved back to Singapore.

Evan seemed all right initially. But soon, Ms Kho noticed that he was putting on weight, getting defensive and taking things too seriously. He cried often and was extremely sensitive to what people said about him.

"Once he wrote me a note which said: "Help me, Mommy. I'm very lonely."

Friends told her it was normal and that he was just going through puberty.

But acting on her instincts, she took him to see a psychiatrist who confirmed that Evan had depression, and also suspected the child had Asperger's Syndrome, a neurological disorder on the higher-functioning end of the autism spectrum.

People with the condition find social interactions difficult and often have narrow or obsessive interests, traits which Evan exhibited.

He was put on medication although the psychiatrist did warn that he should be monitored closely as anti-depressants sometimes lead to suicidal thoughts in children. Many anti-depressants carry a black box warning of increased suicide risks.

Although fearful, Ms Kho and the family monitored Evan closely and also arranged visits to other behavioural therapists.

Ms Kho says: "We made a promise to take our medication together. I told him we would get well together."

Evan was dutiful in taking his medication although he once asked his mother: "Doesn't this mean false happiness?"

She recalls: "He said it wasn't real happiness. But I told him we had to try."

About five months later, he took his own life.

The day before it happened, he texted Ms Kho to say that his maths results were not good.

"I told him to try harder as it was his PSLE the following year. We ended the conversation with the usual 'I love you' and 'I miss you'. Everything seemed normal," she recalls.

The next day, he fibbed and told her there was no school. When told he shouldn't lie, he said something was stressing him out at school. He left the apartment, telling the family's helper that he would wait for Ms Kho at the foot of the condominium so that she could take him to school.

When she heard him close the door, Ms Kho felt something was not quite right. She told the helper to get him back into the apartment but he was nowhere to be found.

Panic set in; she and her helper started combing the estate, calling his name. Then she heard her daughter scream: "Mommy, oh my God."

Her memory of picking up Evan's lifeless body is something Ms Kho can never erase. She is also tormented by the thought that she didn't do enough for him as a mother.

"My logic and intelligence, which had been the basis and foundation of my life for so long, have deserted me, and cannot help me deal with my emotions," says Ms Kho, who is now seeing a counsellor weekly.

But she is determined that Evan's death is not in vain.

Dr Ong Say How, senior consultant and chief of the Department of Developmental Psychiatry at the Institute of Mental Health (IMH), says: "There isn't a centralised system in Singapore which keeps track of data on all children diagnosed with depression in the public and private hospitals and clinics. But from 2013 to 2016, IMH's Child Guidance Clinics, which see patients aged six to 18 years old, saw an average of 190 new patients per year with depression."

Depression, he adds, can strike at any age. Citing a 1996 review paper by Dr Boris Birmaher, an international expert on mood and anxiety disorders in children and adolescents, he says that prevalence rates of depression range between 0.4 per cent and 2.5 per cent in children and between 0.4 per cent and 8.3 per cent in adolescents.

Several psychiatrists The Sunday Times spoke to say growing up can be challenging for many children and teens as they experience bodily changes and grapple with identity and existential issues.

Parents should take heed if their children display certain tell-tale signs, from irrational and bizarre behaviour to changes in appearance and expressions of hopelessness and helplessness, and seek help from a professional counsellor or psychiatrist.

Veteran psychiatrist Munisada Winslow says children with Asperger's are at higher risk of depression. "They have narrow and obsessive interests and can't read social cues but they so want to have friends. And kids can be really harsh. They can make fun of you or bully you or totally ignore you, which is even worse."

Right now, Ms Kho's priority is to keep her other children safe. Her second child, who is seeing a counsellor, has shown signs of insecurity and sometimes wakes up from nightmares crying: "Gor gor (big brother), please come back."

Ms Kho says: "What I took for granted, I don't anymore. I was with Evan that morning, and just like that, he was gone. Now, every hour, every minute with my children counts."