From what I know, I've assisted quite a few relatives and friends with applications, they really do consider the diagnosis, treatment and your own narrative as a whole.
So, if you're prescribed a minimal dose of anti-depressants, have no psychological or psychiatric input and your narrative is that of someone with the equivalent of chronic depression/anxiety they will see right through that and refuse you.
An example of this was for a relative of mine had lung cancer and, thankfully, had the tumour successfully removed. Post-op, dis day-to-day symptoms, honestly described, were rejected based on the DWP's expectation of how he should have recovered, ongoing treatment/monitoring etc. We thought that was harsh, because his symptoms were as described. However on reflection we see why they reached that conclusion.
Fast forward a couple of months, my relative had repeatedly refused to see their GP but was eventually press-ganged into doing so. Investigations identified they have COPD and Emphasymia. Submitted a change of circumstances notification, and they have now been awarded enhanced on both elements because their diagnosis and treatment matches their narrative/experience.
The point here is you can tell them the truth but without evidence of diagnosis and treatment for that diagnosis, they will chase you. They are not fools despite what people believe. Remember, they know what the typical symptoms/impact of conditions are on people and any attempt to over-egg that pudding by describing only your worst days will get their hackles up because, in effect, you are attempting to take them for a fool.
And, yes, the worse you paint your picture the more danger there is of you being charged with fraud if they investigate you. Claiming to be, say, unable to leave the house unescorted and then, say, observed on a daily basis, on your own, taking your child to nursery will see your benefits suspended, you interviewed under caution and, most probably, charged because you won't be able to deny the evidence of pictures of you trotting along the street with the buggy on a daily basis.