Osteoarthritis (OA) is the most common type of arthritis. OA tends to occur in middle age or due to an injury or obesity.

OA can affect any joint, but it typically occurs in the hands, knees, hips, lower back and neck.

NICE CKS - Osteoarthritis

Obsessive-compulsive disorder (OCD) is an anxiety disorder where a person has obsessive thoughts and/or compulsive activity (commonly both).

• An obsession is an unwanted and unpleasant thought, image or urge that repeatedly enters a person's mind, causing feelings of anxiety, disgust or unease.
• A compulsion is a repetitive behaviour or mental act that someone feels they need to carry out to try to temporarily relieve the unpleasant feelings brought on by the obsessive thought

Other anxiety disorders include PTSD and GAD.

Source: NHS Inform - OCD

NICE CKS - OCD

'Overdose' can be abbreviated to 'OD'.

Obstructive sleep apnoea (OSA) occurs when the walls of the throat relax and narrow or close during sleep, interrupting normal breathing. This disturbs sleep.

When asleep, OSA may cause snoring and snorting alongside interrupted breathing. When awake, OSA causes excessive daytime sleepiness (hypersomnia). Hypersomnia poses a danger to driving and should be reported by patients and explored by doctors - the driving licencing/regulatory agency (such as the DVLA) should be informed.

NICE CKS - OSA

Occupational therapy (OT) is an AHP.

OT provides support to people whose health prevents them from doing activities or the occupation they wish to do.