Changing ORDER BY direction causes performance issue
If the different categories you are searching on are not to many and you can build the more complex query, this will use an index on (category_id, newsstudio_id) and I'd expect it to  be more efficient than your previous query, with either ASC or DESC choice.

It's a bit more complex to construct and I'd expect efficiency to degrade if the number of categories are tens or hundreds:

SELECT newsstudio_id
FROM 
  ( ( SELECT newsstudio_id  FROM newsstudio_categories  WHERE category_id = 1303
      ORDER BY newsstudio_id DESC  LIMIT 5 
    ) 
    UNION 
    ( SELECT newsstudio_id  FROM newsstudio_categories  WHERE category_id = 1313
      ORDER BY newsstudio_id DESC  LIMIT 5 
    )
      ...
    UNION
    ( SELECT newsstudio_id  FROM newsstudio_categories  WHERE category_id = 632
      ORDER BY newsstudio_id DESC  LIMIT 5 
    )
  ) AS tmp
ORDER BY newsstudio_id DESC
LIMIT 5 ;