Someone arrives describing poor concentration, low mood, exhaustion and a sense of failing at things they should be able to do. Every one of those symptoms is compatible with at least three explanations, and the explanations interact.
This is one of the genuinely difficult problems in assessment, and it is worth understanding, because the order of things changes what should be treated.
The two directions
Low mood impairs attention. This is a core feature of depression, not a side effect. Concentration, processing speed and working memory are all directly affected, sometimes prominently enough that the cognitive complaint is what brings someone in. Anxiety does something similar by a different route: it occupies working memory continuously, leaving less for anything else.
Attention difficulty produces low mood. Also well described. Two decades of missed deadlines, near-misses, half-finished projects and being told you are not applying yourself reliably produces a set of beliefs about your own competence, and an anxiety that is entirely rational given the history. This is sometimes called demoralisation, and it responds to different things than primary depression does.
So both directions are real, and in many people both are operating.
Why the direction matters
Because treating the downstream thing alone produces partial improvement that gets read as failure.
Treat the depression in someone whose low mood is largely the consequence of a lifetime of untreated attention difficulty, and the mood lifts somewhat while the engine keeps running. The near-misses continue, so the demoralisation returns. The conclusion drawn — by the person, and sometimes by the clinician — is that treatment did not work.
Treat the attention in someone whose difficulty concentrating is a symptom of a depressive episode, and you may be aiming a stimulant at a problem that would resolve with treatment of the mood. That is not a neutral error.
The questions that help untangle it
None of these settles it. Together they are most of what a clinician is working with.
How far back does the attention difficulty go? The single most useful question. Attention difficulty present since school, across settings, in good periods and bad, is a long-standing pattern. Attention difficulty that began alongside the low mood, two years ago, is a different proposition.
Was the attention difficulty present during good periods? If there have been genuinely good stretches — mood fine, life going well — and the difficulty starting things was still there, that is informative.
Is enjoyment lost, or is it blocked? A distinction people find useful. In depression, the capacity for pleasure is reduced — the thing you used to love does nothing now. In attention difficulty, the interest is intact and the access is not: you still want to play the guitar, you just cannot get yourself to pick it up, and when you do it is as good as ever.
Is it worse in the morning or the evening? Not definitive, and worth noting. Classic depressive patterns often include mornings being worst. Attention difficulty tends to track differently — often related to depletion through the day.
What does the sleep look like? Early morning waking with an inability to return to sleep is a particular pattern. Difficulty getting to sleep because the mind will not stop is another. They are not the same clue.
What do other people say? Family who describe someone as "always been like this, since she was six" are giving you a history that is hard to obtain any other way.
The third possibility
Sleep. It deserves its own mention, because insufficient or fragmented sleep produces low mood and impaired attention and fatigue, and sleep apnoea does it reliably and treatably.
It is entirely possible for a presentation that looks like depression plus attention difficulty to be substantially untreated sleep apnoea. Anyone assessing this picture without asking about snoring, waking unrefreshed and daytime sleepiness has left out a common answer.
The same applies, less dramatically, to thyroid function, iron and B12.
What a reasonable approach looks like
Often: treat the clearest and most treatable thing first, and reassess.
If sleep is disordered, fix that and look again — the picture may change substantially. If the depressive episode is prominent and recent, treating it first and reassessing attention afterwards is a defensible sequence. If attention difficulty has been continuous since childhood and the mood is more recent and looks consequent, treating attention may lift a great deal of the mood.
This is iterative rather than diagnostic, and it is a legitimate way to proceed. What makes it work is a clear statement of what is being tried, what improvement would look like, and when it will be reviewed. What makes it fail is nobody writing down what the plan was, so that partial improvement is neither noticed nor built on.
What you can do to help
The history is where the information is, and you are the only source for it. Worth writing down before an appointment:
- A timeline. When the attention difficulty started, as far back as you can reach. When the mood changed. Which came first, if you can tell.
- Good periods. Stretches when mood was fine — and whether the attention difficulty was present during them. This is unusually informative.
- Whether enjoyment is lost or blocked. Concretely, with an example.
- School. Reports if you have them. Comments about potential and carelessness are historical evidence.
- Family. Anybody who was recognisably similar.
- Sleep. Honestly, including snoring.
None of that diagnoses anything. It does mean the first question is the right question, which is most of what a good assessment needs.