As is ALWAYS - 100% - WITHOUT FAIL the case, the mother will have been suffering from depression prior to the crime. What this signifies is that the mother was being treated for depression, in other words taking prescribed drugs known to cause psychotic episodes and linked to hundreds of similar cases of murder, infanticide and suicide.
We have an aggressive pharmaceutical industry, which dreams of having every one of us diagnosed with something, and once you're taking their pills, the only way to get off them is by reducing the dose over a long period of time - or else you risk complete mental chaos.
We have a degenerate society, wherein people live unfulfilling lives, which should rightly make them miserable to contemplate, but this is not depression, and should not be treated as such by doctors. Digging the garden or sitting in the sunshine will do better to raise your spirits than any pill.
This is not to deny people suffer from mental breakdown, which drugs can help to repair. Nevertheless, the dangers of these drugs must be properly acknowledged and doctors and drug companies must change their behaviour.