Mr McLean has been missing since about 3pm on Thursday, October 13, when he left Wakari Hospital.
The 63-year-old has schizophrenia and dementia.
Search and Rescue co-ordinator Sergeant Richard Panting it was still an active search but ``very much in a scaled-back phase''.
``We're basically pretty confident we've covered the areas on the ground of high probability to a high level and as a result we're not putting any more volunteers out until we get more information.''
There was a big push of search parties using volunteers last week from Monday to Thursday, but searches now consisted of an officer and dog exploring ``hot spots''.
The rescue team was working in the hope they would still be able to find him alive, Sgt Panting said.
``Although we know if he was in the bush the likelihood of him surviving this long would be severely reduced if he wasn't supported in some way or another.
``We still have pretty grave concerns for his welfare, having been without medication for this time.''
Any information would be welcomed by police, he said.
``Anything that seems out of the ordinary, clothes or a slipper, we will actively investigate that and it could be the start point we need to ramp things up again.''
The search was being peer-reviewed to ensure no areas were missed, he said.
``Obviously we've focused on the Wakari Hospital Grounds and Frasers Gully in behind that and all the surrounding neighbourhoods, but it's difficult to say how far he could have gone.
``Unfortunately we don't have much to work with in terms of places he was interested in,'' Sgt Panting said.
Dunedin police (03) 471-4800.
