I think the answer is NO as it applies to seeking employment. Here is some information I goggles that is specific to the definition and interpretation of disabled the UK.

http://www.opsi.gov.uk/acts/acts1995/ukpga_19950050_en_3
Great Britian's Disability Discrimination Act 1995 says in part...

Meaning of “disability” and “disabled person”
(1) Subject to the provisions of Schedule 1, a person has a disability for the purposes of this Act if he has a physical or mental impairment which has a substantial and long-term adverse effect on his ability to carry out normal day-to-day activities.

4 Discrimination against applicants and employees
(1) It is unlawful for an employer to discriminate against a disabled person—
(a) in the arrangements which he makes for the purpose of determining to whom he should offer employment;
(b) in the terms on which he offers that person employment; or
(c) by refusing to offer, or deliberately not offering, him employment

http://www.diversityandequality.stir.ac.uk/documents/appendix1.pdf
An interpretation fo the Act says in part........

Appendix (i) The Meaning of Disability (Disability Rights Commission, The Duty to Promote Disability Equality, Statutory Code of Practice, Scotland)
A person has a disability if he or she has a physical or mental impairment, which has a substantial and long-term adverse effect on his or her ability to carry out normal day-to-day activities.
People who have had a disability within the definition are protected from discrimination even if they have since recovered.
It covers physical or mental impairments; this includes sensory impairments, such as those affecting sight or hearing.
The term ‘mental impairment’ is intended to cover a wide range of impairments relating to mental functioning, including what are often known as learning disabilities.
A substantial adverse effect is something which is more than a minor or trivial effect. The requirement that an effect must be substantial reflects the general understanding of disability as a limitation going beyond the normal differences in ability which might exist among people.
A long-term effect of an impairment is one:

Effects which are not long-term would therefore include loss of mobility due to a broken limb which is likely to heal within 12 months and the effects of temporary infections, from which a person would be likely to recover within 12 months.
If an impairment has had a substantial adverse effect on normal day-to-day activities but that effect ceases, the substantial effect is treated as continuing if it is likely to recur; that is if it is more probable than not that the effect will recur.
They are activities which are carried out by most people on a fairly regular and frequent basis. The term is not intended to include activities which are normal only for a particular person or group of people, such as playing a musical instrument, or a sport, to a professional standard or performing a skilled or specialised task at work. However, someone who is affected in such a specialised way but is also affected in normal day-to-day activities would be covered by this part of the definition. The test of whether an impairment affects normal day-to-day activities is whether it affects one of the broad categories of capacity listed in Schedule 1 to the Act. They are:
Someone with an impairment may be receiving medical or other treatment which alleviates or removes the effects (though not the impairment). In such cases, the treatment is ignored and the impairment is taken to have the effect it would have had without such treatment. This does not apply if substantial adverse effects are not likely to recur even if the treatment stops (i.e. the impairment has been cured).
Are there any other people who are automatically treated as disabled under the Act?
Anyone who has HIV infection, cancer or multiple sclerosis is automatically treated as disabled under the Act. In addition, people who are registered as blind or partially sighted, or who are certified as being blind or partially sighted by a consultant ophthalmologist are automatically treated under the Act as being disabled. People who are not registered or certified as blind or partially sighted will be covered by the Act if they can establish that they meet the Act’s definition of disability.
Are any conditions specifically excluded from the coverage of the Act?
Yes. Certain conditions are to be regarded as not amounting to impairments for the purposes of the Act. These are:
Also, disfigurements which consist of a tattoo (which has not been removed), non-medical body piercing, or something attached through such piercing, are to be treated as not having a substantial adverse effect on the person’s ability to carry out normal day-to-day activities.

To make a long story short... Legislation governing 'persons with disabilities' ensures employers don't discriminate and where reasonable accommodations need to be made for employment to be possible employers are expected to accommodate.

Mental impairment is considered a disablility but if you read the Act, the provisions and interpretations there is no reference to mental illness. At best it is an open question as to whether or not mental illness would be interpreted as a mental impairment.

My suggestion is that you consider the language..... a substantial and long-term adverse effect on his or her ability to carry out normal day-to-day activities. That would be the measurement that you would apply when answering the question of disability and it would need to be confirmed by a doctor.

You may be diagnoised with a metal illness but being classified disabled due to a mental disorder is a different story. It usually applies to those people who are unable to work and will therefore need some form of long term private insurance disability income or public social assistance.

Even if it did qualify as a disability per say the legislation prohibits discrimination on the basis of a disability.

This article brings to light the danger of not pre-disclosing a history of mental illness but she won the case. That reinforces my opinion that mental illness is not a disability as defined by most legislations in North America and in Britain.

ps... I thought the list of excluded were too funny. I guess they are avoiding people who engage in criminal activities getting off with arguements of having mental impairments. Still I thought it was funny. lol