The well-researched article "Is this the 'tobacco moment' for cannabis?" (26 November) brings to light the complex relationship between cannabis and psychosis, where the environment, genetic factors and type of cannabis used all play a role.
Anecdotally, as a psychiatrist at the Leeds Addiction Unit, I find that nearly 60-70 per cent of our patients with psychosis either used cannabis regularly in the past or are current users, claiming that it "helps" them with their symptoms. You have rightly pointed out that the level of THC in the cannabis is crucial to the development of mental health problems.
But unfortunately, the story does not end at psychosis. There is also evidence to implicate cannabis in low mood, anxiety and panic attacks. Not only can these symptoms occur as an effect of cannabis while using but also as a withdrawal symptoms when users are weaning themselves off. As a result, they wrongly attribute clinical benefit to cannabis use. This then becomes a vicious cycle and they become more and more habitually dependent on cannabis.
The use of cannabis is higher in teenagers and people in their early twenties. Keeping this in mind, our unit has launched a confidential students' drop-in clinic to offer education around the hazards of drug and excessive alcohol use.
There is a vast unregulated internet market which is expanding every day. There needs to be more legislation around it to bring this trade within the loop of the criminal justice system.
I hope Patrick Cockburn's articles help to educate our public about the drastic ramifications of psychosis which has been precipitated by cannabis.
Dr Yasir Abbasi
Consultant Psychiatrist in Addictions, Leeds and York Partnership NHS Foundation Trust
Don't leave us a legacy of climate chaos
On Monday, as flood waters rose across the UK and as government representatives arrived in Doha for the UN climate change talks, we met with Ed Davey, the Secretary of State for Energy and Climate Change, in Parliament.
We told him that despite the fact that children are not responsible for causing climate change, they are the ones that are most vulnerable to its effects. We asked him to do all he can to ensure that the needs of the world's children are not forgotten in Doha and reminded him that his generation have a responsibility to fix the problem for the sake of our generation and generations to come.
Committing our fair share to the Green Climate Fund and encouraging other nations to do the same will be an important step along this path.
Esme Wedderburn Christa Grayling Lesziah Goodwin
Stella Rousham Hansen Burton
Zoe Nicolaas-Parker Rianna Gayle
UNICEF UK Schools Campaign Network, London EC1
I strongly support the plea for sustainable urban drainage systems (SUDS) (Letter, 24 November). As things stand now, the prospect of floods and the damage they cause will continue. The cost to those concerned, insurers as well as households, businesses and public services, will rise.
In addition to SUDS, there should be a further examination of what might be achieved by cloud seeding, a technique whereby tiny particles are scattered into stormclouds to promote precipitation. Most of the recent references on the world wide web are from the USA. China is believed to make wide use of cloud seeding but there seems to be nothing from western European countries, including the UK.
Forecasters show us the path of low-pressure systems tracking their way across the Atlantic Ocean. There should be trials of cloud seeding to establish whether it is cost-effective to promote precipitation over the sea before the "low" reaches the British Isles.
James F Barnes
The Victorians dredged rivers regularly, without the sophisticated machinery we have today. Dredging will lower the bed of a river, allowing space for rainwater to flow. The silt brought up from the riverbeds will be a rich substance to fertilise our fields.
Since Victorian times more and more silt has formed on the base of our rivers, making them shallower with each passing year.
I'm not likely to be affected by flooding, but it breaks my heart to see people go through such misery each time. Of course the other scandal is how planning permission is still being given to build on flood plains.
Eastbourne, East Sussex
Pickled sharks high and dry
And so, like many tinpot tyros before him, that shooting star, Damien Hirst, sinks into obscurity ("Prices plummeting, lustre fading", 27 November). And all he did was to find himself, a young, ambitious and untalented student, suddenly bundled into the red-hot express lift of the art market for putting a shark in a tank.
We appear to suffer from a belief that if we have the words "artists" and "art" there must therefore be good art being made. But perhaps we should just grow up and admit that we are going through an extended period of banality disguised as art, none of which calls for the ridiculous hype surrounding it.
Only the Church of England
The Church of England is not Britain's established church (leading article, 21 November). It is the established church in England. The Welsh thought better of the principle of a state church as long ago as 1914.
The vote against women bishops makes it even more unacceptable that we tolerate privileged representation in the House of Lords on the basis of discrimination for one faith group among many and from only one part of Great Britain and Northern Ireland.
Hywel Williams MP
Plaid Cymru, Arfon
House of Commons
Reading your article "Half of the clergy opposed to women bishops were women" (27 November), I was reminded of a colleague, an inspector in the Inner London Education Authority, who used to send spoof policy statements through the internal post to headteacher friends of his. Written on ILEA-headed paper, they were crazily similar to the genuine policy documents we regularly received, and brightened our days considerably.
One example ("Equal Opportunities Implications of Staff Appointment Interviews") ended with the pithy, and obviously still relevant, observation: "Remember. A woman is always at a disadvantage when being interviewed by a man. Also when being interviewed by a woman."
On Monday you reported on the red clothes required by newly appointed cardinals and on following pages about Valentino's ladies in red. Does the coincidence presage a move by the Pope, taking advantage of the disarray in the Church of England over women bishops, to make a pre-emptive strike by appointing the first lady cardinals?
Reassurance over genetic tests
Julian Baggini's article on 20 November on the use of genetic information by insurance companies is misleading.
People need to put their health first. If a doctor says someone needs a test then they should take a test. Insurers do need to know about diagnostic tests, but people need not worry about whether insurers use predictive genetic test results – they don't, unless the test was for Huntington's Disease and the customer wants life cover worth more than £500,000. To suggest otherwise could result in people not taking tests that could have a positive impact on their health. This consumer protection is through an established agreement between the Association of British Insurers and the Government.
Rather than "a reason for regulating insurance", this is an example of the insurance industry self-regulating, in partnership with Government, for the good of society.
Association of British Insurers
Austerity is not a luxury
The sting in the tail of Owen Jones' article on austerity (20 November) is the choice between austerity as penance and austerity with a purpose.
If and when we start to make more of what we consume, we will lose the subsidy of cheap developing-world labour and cheap undeveloped-world property costs. Consequently, we will have to work more and consume less. Austerity with a purpose.
Austerity programme re-named: chilly con Carney.
All right? Hard to say
I read Rosalind Grant's letter (22 November) with interest. I too have cancer and am having radiotherapy every day for four weeks. I have noticed that almost without exception when patients are asked by staff how they are today the answer is "Fine", "Not bad", " Good" and so on.
Is this a case of the British stiff upper lip, or are we all just aware that we're all feeling rough but to varying degrees? Perhaps Rosalind could reply to "Y'alright?" with "Still here," which I find seems to cover it.
Holmfirth, West Yorkshire
Clem McCartney's letter (27 November) about "Right?" reminds me of similar greetings in France: "Ça va?" "Ça va!", repeated as often as necessary.
Steeple Claydon, Buckinghamshire
Your leading article of 26 November describes the Prince of Wales as "someone whose most notable life achievement was to be born first in line to the throne." Prince Charles was born second in line to the throne.
Lower Largo, Fife
A hundred and forty characters on a bird? ("WWII code experts called in to mystery of the pigeon's foot", 24 November.) Obviously an early tweet, so unless it is libellous it can safely be ignored.