Codependence: A Big, Big, No-No
- The Underdog
- Jan 26
- 4 min read
Updated: Feb 1
A Little History
The technical term is “Littermate Syndrome*,” but we prefer “codependence,” because relation by blood is not a required factor. Textbook LS refers to two puppies from the same litter. However, this issue shows up in puppies from different litters, and puppy-adult pairs.
It can even occur between two adult dogs, though this is less common. Codependence is by FAR one of the biggest issues we see in multi-dog households.
*It’s also worth noting that Littermate Syndrome is not an actual syndrome by definition.
What Is Codependence?
In short, the dogs are unable to regulate their own emotions and behavior. It occurs when two dogs develop their primary bonds with each other instead of with their humans.
Such pairs become hyper-attached, leaving no room for any human-dog relationship. It usually develops when one or both of the dogs are young (<6 months), but can occur in dogs of any age. Because it’s more common in puppies, that is the age we will focus on here.

Signs of Codependence
...Generally
Dog aggression
Human aggression
Leash reactivity
Fear of the world
Lack of confidence
Anxiety, nervousness, or general inability to relax
Shutdowns or violence in new situations
...When the Dogs Are Together
Rough or insistent play, even when one dog is clearly “done”
Fighting, sometimes to the point of drawing blood
Policing each other’s behavior
Stealing or resource guarding food or toys
...When the Dogs Are Separated
Screaming
Separation anxiety
Refusing obedience
Lunging on leash
Doing anything to get back to one another (anywhere from scratching at the door to
chewing through the wall)
Is Codependence In Dogs Bad?
Yes. Obviously, issues like aggression are difficult, stressful, and dangerous. But some dogs don’t have THAT level of codependence (yet). In most cases, it begins with more mild issues like howling or separation anxiety.
So, if your dogs are “just howling” when separated, should you make the effort to change it?
YES YES YES YES YES YES YES YES YES YES YES YES
These are the first signs that your dogs are about to make your life a living hell. Left unaddressed, dogs will manage their relationship in their own animalistic way. Codependent dogs depend on each other instead of you. Without human guidance, they only learn immature (and potentially dangerous) socialization and boundary skills. This can result in fear, aggression, and violence, among other issues.
In the worst cases, the dogs fight each other TO DEATH. We cannot overstress the seriousness here.

Does Codependence Lead To Aggression?
Codependence is a result of the owner’s failure to teach independent thinking and emotional control.
This means the dogs don’t develop necessary cognitive and emotional skills.
Such dogs are often impulsive, reactive, loud, disrespectful, anxious, nervous, and violent, among many other negative traits.
Riddle me this: what happens when two impulsive, reactive, loud, disrespectful, anxious, nervous, and violent, dogs are left to make their own decisions? We’ll give you a hint: it’s bad.
You’ve essentially created animals with infant emotions but adult strength. They thrive on each other’s emotions, and a startle can devolve into a bloodbath.
In puppy-adult pairs, one of the dogs may have received some independence. In situations including two puppies, both dogs are mentally and emotionally immature. This is why two puppies tend to get particularly extreme.
Yes. Codependence Can Lead To Aggression
Some puppies are raised with other dogs without an issue, which is why codependence isn’t a guaranteed “syndrome” of owning multiple dogs.
However, if we know the potential outcomes, why are we risking it? It is not “easier” to let the dog raise the puppy. Especially if it results in fights, injuries, rehomes, or death.
The risks are too high. If the risk of codependence is even 10%, we should be doing everything in our power to avoid it. It is only fair to everyone involved — dogs and humans.

How to Avoid This Nightmare
Getting Two Puppies at Once
This one is simple: don’t. Dogs should have a minimum of 1 year separation to avoid forming codependence. Ethical breeders and shelters won’t sell two puppies to one buyer for exactly this reason. If someone is offering a BOGO on puppies, hit the road fast af, boy.
Adding A Dog (>6mo) to A Household
Prevent codependence from developing, it’s that simple. We recommend separating adult dogs for a minimum of 30 days. Follow the tables on the downloadable file, and get a trainer.
Take this time to work on obedience with each dog separately. You must form a 1:1 bond with each dog.
Adding A Puppy (<6mo) to A Household
Prevent codependence from developing, it’s that simple. We recommend separating adult dogs for a minimum of 6 months. Follow the tables on the downloadable file, and get a trainer.
People often lament on how annoying this management is, but we can guarantee it is far less annoying than coming home to a dead dog. Take this time to work on obedience with each dog separately. You must form a 1:1 bond with each dog.
We Can't Avoid It — We're Already In It!
Get a trainer immediately. Each case will require different treatments. Some may be manageable with training, others may require rehoming.
You are, in no world, required to keep both dogs because “you made a commitment,” or for any other reason. The primary rule for owning dogs is that you agree to do what is best for the dog(s). This sometimes means rehoming them.
Comments