Dog Anxiety and Behaviour Changes: How to Track What You're Seeing

Behaviour is often the first thing that changes when a dog is unwell. Before there's a visible limp or a missed meal, there's often a quietness - a dog who doesn't come to greet you with the usual enthusiasm, who moves a little more carefully, who's less interested in the toy they normally carry around the house.

We're good at explaining these things away. Off day. Getting older. Bit tired. And sometimes that's true. But behaviour change is also one of the most reliable early indicators of illness, pain, and neurological change - and it's worth taking seriously.

The health-behaviour connection

Pain rarely announces itself as obvious distress in dogs. Many dogs in significant pain show it primarily as behaviour change: less engagement, less willingness to play, reluctance to be touched in certain areas, unusual snappiness when handled. A dog who's been friendly and tolerant with children for years and suddenly growls when a child reaches for their back end is often in pain, not "going off" children.

Urinary tract infections commonly present as house-training accidents in dogs who have been reliable for years. The dog isn't being naughty - they have a medical problem that makes holding their bladder difficult. This is especially common in older dogs and in females.

Thyroid conditions can affect temperament. Hypothyroidism can cause lethargy and reduced mental sharpness. Some research suggests that in rare cases, thyroid dysfunction may contribute to aggression.

Cognitive dysfunction syndrome - canine dementia - produces behaviour changes before physical changes in many dogs. Confusion in familiar environments, disrupted sleep, reduced interaction, apparent forgetfulness, house-training regression. These changes often start subtly and are attributed to "just getting old" when they may be a diagnosable condition with management options.

Neurological conditions including spinal cord disease, brain tumours, and vestibular syndrome (inner ear) can all produce sudden behaviour changes, disorientation, and changes in gait.

The practical implication: if your dog's behaviour changes in a way that's new, unusual, or persistent, a health check should precede behavioural explanations. The PDSA PAW Mini Report 2025 found that 1.6 million UK dogs (around 16%) show signs of fear, growling, or biting towards people - underlining how common behaviour-based presentations are, and how often they have an underlying health component that goes unaddressed.

What to log

Write down what you're seeing, when it started, and whether it's getting better, worse, or staying the same:

• What changed: be specific - "more withdrawn than usual", "growled when I touched his back end", "didn't meet me at the door this morning", "slept all day"
• When you first noticed it: a date, or an approximate ("about two weeks ago")
• Whether anything preceded it: a new medication, a change in routine, a trip to kennels, a stressful event, an injury you witnessed
• Whether it's improving or worsening: or fluctuating - some days better, some worse
• Accompanying physical signs: any changes in appetite, water intake, mobility, bathroom habits

Video is often more useful than written description for behavioural concerns. A thirty-second clip of your dog walking after rest, or behaving unusually in a specific situation, gives a vet far more information than a description of the same thing.

Distinguishing medical from behavioural

Some behaviour changes have obvious situational causes - a dog who became fearful of loud noises after fireworks, or one who started resource-guarding after a new dog joined the household. These are behavioural in origin and benefit from behavioural intervention.

Others have no obvious situational cause, or started suddenly rather than gradually. Sudden behaviour changes - particularly in a dog with no history of that behaviour - are more likely to have a medical component.

The general rule: rule out medical causes first. A dog who snaps when touched might need a pain assessment before any behavioural work. A dog who starts having accidents might need a urine test before any retraining.

Anxiety in dogs

Genuine anxiety - as distinct from a specific fear triggered by a specific thing - is increasingly recognised in dogs. The PDSA PAW Mini Report 2025 found that 19% of UK dogs are left alone for five or more hours on a typical weekday - significantly more than the 15% recorded in 2022 - which the report links to rising levels of separation-related distress. Signs of anxiety include:

• Panting at rest in cool conditions
• Pacing, inability to settle
• Excessive attention-seeking or clinginess
• Yawning, lip-licking, yawning as stress signals throughout the day
• Destructive behaviour when alone
• Reduced appetite in situations that cause stress

Anxiety can have a medical component (pain, hyperthyroidism, some neurological conditions), a genetic component (certain lines and breeds carry higher anxiety risk), an environmental component (early life experiences, trauma), or some combination of all three.

Medical causes should be ruled out first. After that, the two most useful approaches are: working with a clinical animal behaviourist (particularly one with veterinary training), and considering whether medication is appropriate - there are effective pharmaceutical options for anxiety in dogs that work best alongside behavioural modification.

When a log matters most

See our dog anxiety condition guide for a full breakdown of what to monitor, severity scoring, and how to structure a behaviour log your vet or behaviourist can use.

The value of a behaviour log compounds over time. A single entry that says "seemed quieter than usual today" doesn't tell you much. Twelve entries over three months that all say some version of "quieter than usual, less interested in the walk, slower to get up" tell you a story.

That story is what helps a vet determine whether what you're seeing is progressive, whether it correlates with a new medication, whether it's worsening - and whether it warrants investigation.

Frequently Asked Questions

My dog has suddenly become aggressive after years of being gentle. Should I go straight to the vet? Yes. Sudden-onset aggression in a previously non-aggressive dog is one of the clearest indicators of a pain or medical cause. Before any behavioural work, a full physical examination - including pain assessment, blood tests, and potentially imaging - should be done. Pain is among the most common medical causes of aggression in dogs.

My dog's personality seems to have changed as they've got older. Is that normal? Some mellowing with age is normal. Significant changes - reduced engagement, confusion, altered sleep patterns, loss of previously reliable behaviours - are not simply "getting old" and warrant assessment. Cognitive dysfunction syndrome is a real and treatable condition.

Can separation anxiety come on suddenly in a dog who was previously fine? Yes. A major change in routine - owner returning to office work after a period at home, a new baby, a move - can trigger separation anxiety in a previously settled dog. Illness can also reduce a dog's ability to cope with things they previously managed. A gradual desensitisation programme, ideally with professional guidance, is the most effective treatment.

How do I know if my dog is in pain without them obviously limping or yelping? Subtle pain signs include: reluctance to be touched in certain areas, changes in posture (hunching, tucking the tail), reduced activity or play without obvious cause, changes in facial expression (tight muscles around the eyes and forehead), and behaviour changes like the ones described above. Dogs are stoic - they don't complain loudly the way humans might.