This was originally going to be a response to Funky-Butt's post 'Euphoria when starting pred..', but it was turning into a 3-volume novel and I realised that I've never heard of anybody else reacting quite the way I did and thought it might merit a separate post.
I was first prescribed 60 mgs of pred per day and the rheumy asked me to come back to see her in a fortnight and to come in for blood tests on the Friday before I saw her. She also warned me that I might feel very depressed and to seek help if I had any symptoms of that kind. Like others I felt euphoric rather than depressed at first. I'd describe my state of mind as being similar to that just after childbirth when emotions are very raw.
When I went back for the blood tests, I got very angry about a selfish woman who went out to take a phone call just before her number came up, upset the queuing system and was rude to the staff when she came back. When I went in for my turn, I collapsed against the wall with the most excruciating frontal headache that I've ever had. This was followed by an hour of intermittent vomiting in the ladies' loos with my head in turmoil. Somebody got help and I was examined by the triage nurse, who clearly thought at first that I might be having a stroke as my speech was very confused, or I was possibly an escapee from the dementia ward. When they sorted out my medical records and I became a bit more lucid, the doctor said he wanted to keep me in for the weekend. My daughter was there by that time and we asked if it could be the effect of the steroids and he said 'No, steroids have lots of possible side effects but this isn't one of them.' I was given all sorts of tests over the weekend including a lumbar puncture and discharged feeling much better, but none the wiser about the cause. When I saw the rheumy for my second appointment, she was also dismissive of the idea that it might have been the steroids.
A few days later I was at home with a friend. We began discussing a very sad story in the news involving cruelty to a small child. I immediately started getting the headache and becoming confused in speech. She called the ambulance, which arrived in less than 15 minutes. The paramedics gave me the once over - apart from anything else my blood pressure was through the roof. They took me to A&E, where my daughter and I spent most of the night. This time the doctor on duty said that it was the side effect of the pred, that it would eventually wear off and that in the meantime I should avoid anything that was likely to make me emotional.
I can only assume that the first doctor and the rheumy dismissed the idea because they were afraid I'd be tempted to stop taking the pred. If so, I wish they'd treated me like an intelligent adult and been honest.
During the following week or two I did a few times feel the start of a similar headache, including once bizarrely when I was laughing at 'Just a Minute' on the radio. I found that just by relaxing and keeping my breathing shallow for a while, I could control it. It soon passed off completely and I've never felt like that since.