I have had depression on and off for ages, and have been on a kind of maintenance dose of 20mg of citalopram for years, with periodic increases in dose that I reduce again when I can. The increase is usually in the winter (SAD sufferer.) This year I increased to 30 mg 3 weeks back but no improvement so far. Historically I improve quite quickly so a bit thrown by this. Do I just need more? Or do ADs somehow stop working?? Any suggestions or similar experiences would be great, thanks.