To be frank, i have had cats who were outdoor cats, who have due to circumstances needed to adapt to indoor life. They do. It takes time, love and patience with the results of the temporary stress of wanting out - but really, we can't let them out for at least 6 weeks after they have come to us, and by that stage, the worst of it is generally over. If someone is at home during the day, there is lots of enrichment around, and (ideally) the cat has a companion cat, then they cope very well. My mother's cats had had free range over miles of countryside before she moved into a unit - they adapted very well and lived out their lives happily. One of them is now living with my sister and has the option of being an outdoor cat once more, but prefers to stay inside. The other, who had been adopted when mum was in the unit, and who also has outdoor access, is thriving as an outdoor kittie. I really don't understand why it is considered such a challenge, as the indoor cat is healthy, safe from risks such as traffic, other animals and people and they thrive Surely you can't wish for better than that ... Sorry, rant over...