A woman with breast cancer found dead with her seven-year-old son had a strong fear of death, despite having a "likely curable" condition, an inquest has heard.
Yulia Gokcedag and her son Timur were found dead at their home in the Isle of Dogs, east London, on 13 August.
Officers found 35-year-old Mrs Gokcedag hanged and Timur in the bath, Poplar Coroner's Court heard.
Mrs Gokcedag had been given a 97% chance of surviving cancer by doctors.
But she believed she would be among the 3% who did not survive, the inquest heard.
Nathaniel Cary, who carried out Timur's post-mortem examination, said the boy suffered bruising to his scalp and chin, which could have been "consistent with enforced immersion".
Dr Cary said: "It may be that Timur was rapidly overwhelmed while initially passively sitting in the bath."
Financial data analyst Mrs Gokcedag's husband Mehmet gave evidence at the inquest.
He told the court: "She was a good mother. She loved our son and it is very unimaginable why and how she could do this, the child that came out of her - why would she take his life?"
He said his wife had talked about taking her own life in May, speaking about submerging herself in the bathtub and attempting to choke herself.
"She said there was a constant vibration or trembling inside her... she had a fear of death."
The inquest heard Mrs Gokcedag had been diagnosed with breast cancer in January and underwent chemotherapy sessions.
Mrs Gokcedag's post-mortem examination found there were no signs of malignant tumours, with only microscopic traces of a tumour remaining.
Prof Paul Ellis, an oncologist, told the inquest that the 35-year-old had finished chemotherapy and had been scheduled for surgery the week after her death.
Dr Mark Flynn, a clinical psychologist, said Mrs Gokcedag had acute anxiety and a "huge amount of self-recrimination about her possible responsibility for the diagnosis and the course of her treatment".
Asked if Mrs Gokcedag had ever shown signs of wanting to harm Timur, Dr Flynn said she had not.
He told the inquest: "She struck me as very warm and loving. He would sometimes come into sessions and they seemed to have a very warm, healthy, tactile connection."
The inquest continues.