Is reactive grief treated the same as long term depression?
No. The high quality life insurance companies make a distinction between a reactive depression to an understandable grief event - for example the death of a partner - and long term generalised depression.
The three keys areas considered are Cause (what was the stressor), Time (how long ago was the event and how long did it persist), and Effect (how were you affected eg: ability to work, time off and outcomes).
This is why you need to work with a specialist risk insurance adviser to help find the right life insurance provider and the right underwriting policies for you and your very personal circumstances so you can have the best chance at getting cover in place.