Any of the above circumstances may find the owners noticing destructive behaviour patterns in their dogs, mood swings from day to day or maybe from week to week, the lack of attention or willingness to learn, the need to revert back to puppy behaviour by soiling their beds or nearby surroundings and the list goes on. Sometimes these signs within the dog are noticed a little at a time with the owners not taking much noticed or giving it much concern, explaining it away as a puppy thing until it becomes a greater problem than they can handle or becomes more consistent to the point that they have to notice or show concern. By then, days, weeks and sometimes months have passed. The latter is the most difficult to determine and to solve because of the time lapse that can occur from when the 'anxiety' first appeared in the dog and to when the owners finally noticed. In most cases the problem signs have gone on long enough that it is no longer just a personality quirk but and bad habit and a real behaviour problem.
Every dog is different as is every owner.
How well an owner reads their dog, how quick they are to recognize any strange signs and how fast they learn to seek help to curb these problems will also vary with every owner. I suggest for those that need the help immediately, seek out a Behavioural Consultant or experienced Trainer to assist you on a more personal basis. To look into this situation a little deeper and find a way to 'prevent' this from happening to you and your dog, please read on. I believe the 'key' to minimizing 'separation anxiety' from occurring is to 'Socialize' your pup at a young age and continuously throughout their life. Do not force but do not buckle under pressure either.